Key Highlights

  • F5 (NASDAQ:FFIV) closed down 20.43% on October 28, 2026 after guiding fiscal 2027 revenue growth to 8% to 9% from 11%. Landstar System (NASDAQ:LSTR) fell about 17% even though revenue rose 25%, with one account citing claims costs.
  • Enphase Energy (NASDAQ:ENPH) closed down 16.03% after guiding fourth-quarter revenue to USD 225 million to USD 255 million, about 18.2% below the USD 293.3 million just reported at the midpoint, simple arithmetic.
  • LPL Financial (NASDAQ:LPLA) fell 15.2% with no announcement or analyst note found. CoStar Group (NASDAQ:CSGP) fell 14% to 15% despite third-quarter revenue of USD 952 million, up 14%, while guidance accounts conflict.
  • Four of the five drops come from earnings reports. The cause is stated by the company for Enphase and F5, comes from one account for Landstar, conflicts for CoStar and is missing for LPL Financial.

F5 (NASDAQ:FFIV): Guidance shock

F5 (NASDAQ:FFIV) said in its company release that it expects fiscal 2027 revenue growth of 8% to 9%, compared with 11% for the earlier period referenced in the material reviewed. The stock closed down 20.43% on October 28, 2026. Simple arithmetic shows the gap: on a base of 100, growth of 11% gives 111, while 8% to 9% gives 108 to 109. That is a revenue shortfall of about 2 to 3 points relative to the earlier pace, which compounds into the following year. The material reviewed did not give the dollar revenue guide, the earnings per share outlook or the quarterly results, so the full picture is incomplete. Investors pay for expected growth, so when F5 (NASDAQ:FFIV) lowers its growth outlook, the multiple the market applies to revenue and profit can compress even if the business remains profitable. A Piper Sandler downgrade, as reported, can amplify this because analysts reset estimates and some funds follow ratings. The mechanism is a feedback loop: lower guide, lower estimates, lower target multiples.

Landstar System (NASDAQ:LSTR): Claims costs, one account

Landstar System (NASDAQ:LSTR) shares fell about 17% on October 28, 2026, according to published market data, after a quarter in which revenue rose 25%. One account attributes the fall to insurance and claims costs that hit earnings per share, which means the cost of accidents, cargo claims and insurance premiums grew faster than revenue. The material reviewed gave no dollar figures for those costs, earnings per share, margins or consensus estimates, so the size of the miss is unknown. The headline contrast, strong sales and a steep drop, shows how much investors focus on profit conversion in freight. Freight brokers and agent networks can also see revenue rise from higher pass-through freight rates without a matching rise in profit, so the 25% figure alone says little about earnings quality. Freight and logistics companies carry liability for accidents and damaged goods, and they buy insurance or self-insure up to certain limits. When claims rise, the expense lands in the income statement in the quarter the claims are recognised, which can cut operating profit sharply. Landstar System (NASDAQ:LSTR) operates largely through independent agents and owner-operators, a structure that keeps fixed costs low, but claims are still a risk.

Enphase Energy (NASDAQ:ENPH): Weak fourth-quarter guide

Enphase Energy (NASDAQ:ENPH) reported third-quarter revenue of USD 293.3 million and guided the fourth quarter to USD 225 million to USD 255 million, according to the company release. The low end is about 23.3% below the third quarter and the high end about 13.1% below, simple arithmetic on published numbers. The stock closed down 16.03% on October 28, 2026, after touching 17.1% lower during the session, while after-hours reports of declines ranged from 10% to 15.7%. Those after-hours figures come from different accounts and conflict, so the close is the more reliable measure of the day. Guidance is management's own forecast, so a figure this far below the last reported quarter is a direct signal about order books. Enphase sells microinverters and related equipment to distributors and installers, and revenue recognised at that step is called sell-in. Sell-through is the next step, when installers sell systems to homeowners. The company said its guidance assumes sell-through 10% below the third quarter.

LPL Financial (NASDAQ:LPLA): No explanation found

Published market data show LPL Financial (NASDAQ:LPLA) down 15.2% on October 28, 2026, the largest of a group of decliners with no explanation found. Tickers EDU and ZWS fell 12.5% and 11.5%. They appear as tickers only in the data reviewed, so their company names and exchanges are not confirmed here and they carry no tags. Baker Hughes fell 7.2%, Banco Santander 6.1% and Garmin 5.7%. The companies span wealth management, education, water products, energy services, banking and consumer devices, which suggests no single industry story ties the moves together. Because none of the moves came with a verified explanation, this article reports only the price changes that published market data show. A sharp fall with no announcement can have several mechanisms, none confirmed here. Results or guidance released after the prior close may not have been captured. An analyst downgrade, a large block sale, index changes or a shift in funding costs can move a stock without a company release.

CoStar Group (NASDAQ:CSGP): Growth with a steep fall

CoStar Group (NASDAQ:CSGP) reported third-quarter revenue of USD 952 million, up 14%, according to the company release, and its shares fell 14% to 15% on October 28, 2026. Reversing the growth rate, the prior-year quarter was about USD 835 million, simple arithmetic on published numbers. The material reviewed did not give earnings per share, margins, cash flow or consensus estimates, so it is unclear whether the quarter beat or missed expectations. The mismatch between solid growth and a steep fall usually means something other than headline revenue disappointed, which makes the reaction harder to explain from the numbers alone. Without consensus numbers, it is not possible to say whether the market saw this as a shortfall. One account says CoStar Group (NASDAQ:CSGP) raised full-year guidance, while another points to weak revenue guidance. Guidance is management's forecast for future results, and markets often react more to a change in that forecast than to the quarter just reported.

Where Things Stand

The answer is that the five biggest losers fell for different reasons, and only two causes are firmly documented. F5 (NASDAQ:FFIV) gave weak guidance. Enphase Energy (NASDAQ:ENPH) did the same. Landstar System (NASDAQ:LSTR) rests on one account about claims costs. CoStar Group (NASDAQ:CSGP) has conflicting guidance accounts. LPL Financial (NASDAQ:LPLA) has no explanation. Nasdaq-100 futures were down about 1.2% at 4:09 a.m. ET on October 29. This is not investment advice.