Pool had a high demand for chlorine all last summer and some staining issues at the end of the summer before I closed it. When I opened it on April 14th I shocked it with 12lbs. of shock (because of chlorine lock issues last opening) and the next morning only had a free chlorine reading of 3. 12 hrs. later fc was down to 1. I shocked again with 8lbs. 24 hrs. later the numbers look like this. fc 3.4 tc 4.5 ph 6.9 ch 70 alk 100 cya 85. I added 6-8 lbs of ph plus in 24 oz dose but every time the ph hasn't changed.I really think most of my problems might be in the shock and algeacide that I am using. Pool brand shock with 99% Sodium Dicloro-s-Triazinetrione, Pool brand algeacide with dimethyl benzyl ammonium chloride. any help with this would be appreciated. Even if the chemicals I am using are the problem, I have no idea where to start to fix this without draining water.