Chris, are you still sometimes adding a little Epsom salts to the sprayer when you feed with the potassium nitrate? That's a good combination, but maybe only do that once a week, or once in a while.
Just so you know, most people only water their Phals about once or twice a week if growing indoors. Since your greenhouse is pretty warm, and your air is pretty dry, more often plus misting is a good thing but - you DO need to let them dry out occasionally. I would pick a couple of days per week when they will get nothing at all - no misting or water. Say, Tuesday and Friday?
How warm do you think it's going to be in your greenhouse at the height of summer? If it's getting much over 90 to 95, it might be wise to think about moving the Phals out to a cooler place in the garden, say under a tree? If not, misting in the afternoon when it's hottest might be a good idea just to cool the plants off.
