The S&P/ASX 200 Index (ASX: XJO) has given back its early gains and dropped into the red. In afternoon trade, the benchmark index is down 0.3% to 7,988.5 points.

Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

Adairs Ltd (ASX: ADH)

The Adairs share price is down 10% to $1.68. This has been driven partly by the homewares retailer's shares going ex-dividend this morning. Last month, the retailer released its full year results and declared a final fully franked dividend of 7 cents per share. Eligible shareholders can now look forward to receiving this payout next month on 8 October. In other news, this morning Adairs revealed that its interim chair, Kate Spargo, has resigned with immediate effect. Ms Spargo had been with the company for 9 years.

Commonwealth Bank of Australia (ASX: CBA)

The CBA share price is down over 1.5% to $141.43. This is despite there being no news out of Australia's largest bank. However, it is worth noting that all the big four banks are tumbling today. Some investors may be taking profit off the table following strong gains. For example, even after today's decline, the CBA share price is up over 38% since this time last year. This is more than triple the market return over the same period.

NextDC Ltd (ASX: NXT)

The NextDC share price is down almost 5% to $16.99. This morning, this data centre operator announced the completion of a $550 million institutional placement. These funds are being raised at $17.15 per new share, which represents a modest 3.9% discount to where the NextDC share price last traded. Combined with a $200 million share purchase plan, the proceeds will be used primarily for the acquisition of new data centre development sites in Asia.

REA Group Ltd (ASX: REA)

The REA Group share price is down 2% to $198.28. This follows news that the property listings company's $11 billion takeover offer for Rightmove (LSE: RMV) has been rejected. Given that the market was unsure about the transaction, with some analysts believing that it was overpaying, the prospect of REA Group returning with a higher offer could be setting off alarm bells. REA Group believes that its "proposal combines certainty of value, in cash, at a significant premium to recent trading while at the same time giving Rightmove shareholders the opportunity to benefit from the future value creation of the combined business." But Rightmove clearly doesn't agree.