It does dissolve before reaching the bottom. It is fine to add sequasol right after the ascorbic acid - and not a problem to add the ascorbic acid after. I would wait a while befor adding more, I think after the water filters for a while it will take the rest of the stain off. You can add more ascorbic acid, but it will just take longer for the pool to hold chlorine. The pool won't hold chlorine till the chlorine eats up all the ascorbic acid that is in the water, that's why I try to use as little as possible. You can even wait till tomorrow to add more if you still have stain. Congrats! you're almost finished!