Within the last couple of weeks I have noticed that my plaster has developed bright white spot as compared to the rest of the pool. The pool is about 1 year old and is 12,000 gallons. When you rub your finger over the plaster it feels smooth. I get my water tested weekly and have ho no major issues. My alkalinity and PH sometime are slightly out of wack but nothing else comes to mind.

Does anyone have any idea what may be casuing this or is this normal???