Ok, I shocked the pool at sundown tonight. I did not add more sequestering agent because I had put in more than the instructions called for already, which could be part of my problem, I now realize. The pool liner guy said I needed to get that sequestering agent in right away because we have so much iron. What I should have done was get chlorine in right away, as the pool was filling, it seems. I must learn not to listen to "pool guys"! I'll keep it at shock level now until things clear up. I'll keep you posted and thanks again for all the great help.