As many have said it may be alk burn, although are any other acros in the tank experiencing swelling at the tips? the flow may have an issue aswell, I would chop the burnt tips off and try all the things suggested... It should recover.
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90g starphire cube/400mhRadium20k/2 XHO/2x27w UV/2x39w T5/ 3 Trulumen led strips
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