What is wrong

[Tailored Aquatics]

Alkalinity seems quite low. If the "100" alkilintiy is in mg/L.

Alkalinity is typically reported as mg/L as CaCO3 (Calcium Carbonate) by Hagen test kits. This can be converted into milliEquivalents per Liter (mEq/L) by dividing by 50.To convert mEq/L (milliequivalent per liter)to dKH multiply by 2.8. To recap the conversion for the three units is: 1 meq/l = 2.8 dKH = 50 ppm CaCO3

so your 100 mg/L divided by 50 = 2 mEq/L
2 mEg/L times 2.8 = 5.6 dKH....quite low, I would bring it up to at least 8 dKH or 145 mg/L and the sps should stop bleaching.