Just tested water. CYA 35, FC 5, Alk 40, pH 7.2, TH 50.

Alk seems low. Should I do something there and if so what? TH also seems low but what do I need to do for that. These test strip readings are quite different from the pool store readings on 8/5/11. Would readings for Alk go from 120 to 40 and Calcium hardness go from 200 to my TH of 50 in 3 days ? I suppose CH and TH are not the same thing?

The CYA I believe to be correct according to the black dot test. Wonder why their reading was so much higher at 60 3 days ago. Only thing I have done is add 2 pucks chlorine. It did rain 2 to 3 inches since their test but that is the only other input to the pool except the very high heat of 100 deg each day.