The coral pro could be causing an alk swing as well if your not testing or wc regularly or manually dosing.
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What are your water parameters? Especially Nitrate, Phosphate, and Alkalinity.
Add Calcium and Magnesium to that list. Coraline Algae (Is purple) and thrives off of calcium. I would bet that may be out of whack. Also has their been any swings. SPS like stable parameters. So make sure to do things slowly.

