Montipora turning tan

Hi all, looking for input. I have a Montipora that has started going from green to tan. It seemed happy for over 6 months and all of a sudden it has started turning. Nothing has changed as far as light. Flow is a bit different since I lost 1 powerhead. It was without it for several weeks.


Parameters all test good and low to no phosphates.


Any ideas what else could have caused this?



Thanks!

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