Stain and scale is for metals - if you don't have metals, don't use it.
High CC doesn't contribute to foam, low calcium could though. High CC is from the chlorine eating up the enzymes.
I was instructed by a dealer on here to put in chlorine the next morning after soaking so thet the enzymes had a chance to work but with the knowledge that the chlorine eats up the enzymes, if I soaked every day then they enzymes would be used up in 3 days or so.
I've stated this in the past, not everyone's water is the same. It might be H2O and the balance might be the same but it seems it reacts differently with everyone.
What I would do is - scoop out the foam, hit the tub with MPS - this will get rid of the CC and any organics that cause foam, stop using enzymes for a while (week or 2) and let what comes naturally happen. It might be that there's nothing in the water to react to.
They claim foaming is a byproduct of the enzyme working but I don't buy that. I had gotten a great deal on ebay for the enzymes and after a while I chucked them!