The S&P/ASX 200 Index (ASX: XJO) is starting the week in a positive fashion. In afternoon trade, the benchmark index is up 1.3% to 8,919.2 points.
Four ASX shares that have failed to follow the market higher today are listed below. Here's why they are falling:
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Aussie Broadband Ltd (ASX: ABB)
The Aussie Broadband share price is down 5% to $5.27. Investors have been selling the broadband provider's shares following the release of a trading update this morning. Aussie Broadband revealed that it expects to report earnings in the middle of the previously announced underlying EBITDA FY 2026 guidance range of $162 million to $167 million. In addition, capital expenditure is expected to be at the upper end of the previously provided guidance range of $55 million to $60 million. This may have fallen short of the market's expectations for the financial year.
Coles Group Ltd (ASX: COL)
The Coles Group share price is down 2% to $23.51. This may have been driven by investors switching out of defensive assets and into risk-on assets. A number of defensive ASX shares are falling on Monday while the market charges higher.
Electro Optic Systems Holdings Ltd (ASX: EOS)
The EOS share price is down 2.5% to $9.10. This follows the release of a revenue update from the defence and space company this morning. EOS revealed that it expects to generate between $240 million and $270 million of revenue in 2026, excluding the recently acquired MARSS business. The high end of this guidance range is over double the $128.5 million it reported from continuing operations in FY 2025. This may have been overshadowed by news that the US and Iran have signed a peace deal, which could potentially mean softer than expected demand for defence products in the near term.
Santos Ltd (ASX: STO)
The Santos share price is down a sizeable 7.5% to $7.46. Investors have been selling Santos and other ASX energy stocks on Monday after oil prices pulled back meaningfully. Traders were selling oil in response to news that the US and Iran have signed a peace deal. Upon the announcement, US President Donald Trump said: "Let the oil flow!" This is great news for the world, but less so oil producers. The S&P/ASX 200 Energy index is down 5% at the time of writing.
