Chris, I looked on all my seven (yes, 7 ! ) different fertilizer packages and only one - the MSU formula - has any calcium in it. This may be because it is formulated to be used with R/O water. I'll bet that if you just misted with your tap (hose) water once a week, that would very likely supply all the calcium your plants need. I've never added any calcium supplement to my orchid regime but my automatic mist system uses well water which has plenty.
Please be sure not to "kill them with kindness" here. You do need to let your plants dry out a bit, even though they like high humidity. I'm only using the Potassium nitrate formula once a week on my Vandas (which are heavy feeders) at the moment. Phals are not fast growers or heavy feeders. I'd advise you ease up on the misting and feeding, and just let them dry out at least every second day.
You can keep the humidity up in your greenhouse without misting the plants - just spray the hose around on the floor, walls, and other surrounding stuff. Clay pots absorb and release moisture, so if you have any plants in clay, spray the outsides of the pots and they will help with the humidity. If that's not enough, hang some old towels in there, and wet them down daily.
I also hang my laundry to dry on hangers around the plants when I have them in the house - usually that's in cold weather which is also dry weather here. Just tumble in the dryer for about 10 minutes then hang up, and distribute. Saves on electricity and humidifies the area as well! A win/win!
