Swimming pools blog

I am new to this group out of necessity…. Yesterday, my pool was
crystal clear… Perfect…. I checked the water and the PH was very
low (like it stayed clear when I put in the red drop)…. So I dumped
in some P-plus. Within 5 minutes, the whole pool looked like milk!
What happened? When I check the PH now, it’s raised only slightly, and
shows within the range of where it should be, but I can’t see the
bottom of the shallow end!
Can someone tell me what to do next?