red spots on filter

[myINpool]

Has anybody ever had red spots on their cartridge filters? I've got cloudy water in my salt pool and noticed the red spots when I went to clean the filters. They are very small, maybe 1/16" from side to side, but all over the filters. My chlorine is slightly low, and I struggle to keep my ph down. I can get my ph down to about 7.8 with acid, but it goes back up in the course of 3 weeks or so. I've also got dark powdery substance on my light. If anybody has ever come across this problem before, please, please advise.

[mRaffa]

The only time I had any red color in my pool is when my son went swimming in the ocean and went into the pool....it took silver algeacide to remove the problem.