OK, I've been testing & adding 1/2 box of Borax at a time (as well as keeping chlorine levels up with bleach), & pH finally started to increase. As of this morning, here are the latest readings:

FC 3.6
pH 7.3
TA 105
CYA 100

Chlorine has been holding fairly steady, & water is still blue, so I think algae is gone. It's still cloudy but I can see further down than before (about 2 feet). I do have a bottle of 60% poly algaecide which I've read in other posts can help. Do you think I should try it?