Sudden pH drop...Why?

[isdsms]

When I open our ig pool several weeks ago the pH level was 7.3. I added a few boxes of borax and got it up to a more desirable 7.6. I continued to check over the next few days and the level stayed good. Just for the heck of it, I check tonight only to find a drastic drop to 7.0. My chlorinator was set a bit too high and the weather has been very hot, but other than that, nothing out of the ordinary. Any ideas what gives???

[Watermom]

Trichlor tabs are extremely acidic and can cause a ph drop.

[CarlD]

Trichlor tabs are extremely acidic and can cause a ph drop.

I came back from a vacation where I had left a number of floaters with tabs in my pool. CYA had gone from 30 to 60 and pH was below 6.8--two boxes of Borax went in immediately.