The S&P/ASX 200 Index (ASX: XJO is back on form and on course to record a strong gain. In afternoon trade, the benchmark index is up 0.75% to 7,346.6 points.

Four ASX shares that have failed to follow the market higher today are listed below. Here's why they are tumbling:

Afterpay Ltd (ASX: APT)

The Afterpay share price is down 2% to $82.60. This is an improvement from earlier in the day when the payments company's shares tumbled to a new 52-week low of $80.21. This followed another heavy decline from the Square share price overnight. This decline devalued the takeover offer that Afterpay shareholders voted in favour of last week.

Humm Group Ltd (ASX: HUM)

The Humm share price is down 5% to 86.5 cents. This appears to have been driven by profit taking after a strong gain on Monday. Investors were buying the financial services company's shares after it revealed that it has received approaches from third parties to acquire all or part of it. No further details were provided but management intends to engage with the would-be suitors.

Namoi Cotton Ltd (ASX: NAM)

The Namoi Cotton share price is down 10% to 46 cents. Investors have been selling this cotton producer's shares after it warned that 2022 could be a difficult year. Namoi Cotton advised that cotton growing areas in NSW and Queensland have experienced flooding in November and December which may result in a loss of crops.

Pilbara Minerals Ltd (ASX: PLS)

The Pilbara Minerals share price is down 11% to $2.46 after downgrading its production guidance. The lithium miner revealed that delays have been experienced with both the Ngungaju Plant re-start and Pilgan Plant Improvements Project. As a result, its FY 2022 concentrate production guidance has been downgraded to 400,000 to 450,000 dmt from 460,000 to 510,000 dmt.

The post Why Afterpay, Humm, Namoi Cotton, and Pilbara Minerals shares are falling appeared first on The Motley Fool Australia.