I could be wrong on this but wihtout a good alkalinty buffer system in place wouldnt the bleach cause the pH to bounce up? Seems like it would make sense to get that done first. Also the bleach is less active at higher pH becuase there is more hypochlorite ions and less hypoclorous acid present.
If it turns green a shock dose of bleach should clear it right up.

anyone got any ideas on this?