Definitely don't add any more of the HTH algaecide--the chlorine you use will eventually break down whatever's causing the smell and the foaming. Remember that algaecides are much better at preventing an algae outbreak than they are at killing an active one--and even then you only want to use Polyquat 60 because of the same problems that you mentioned.

I'll let one of the stain experts advise you on whether it's time to start raising your levels again, but I just wanted to warn you that when you do, do it slowly so that if you start to see browning of your water you can get some sequestrant in there before you end up with staining again. High chlorine and high pH levels are what bring the metals out of solution, so just have that in mind when you start raising your levels.

Janet