I think you're on the money then!!My plants are in plain old field soil. I don't flush anything. I used gypsum, oyster shell flour, Cal-Phos, fish bone meal for the macros and the sulfate forms of the zinc, manganese and copper. I used Borax for boron, sodium molybdate for molybdenum and sodium selenite and sodium selenate for selenium. I have specific mineral ratios I aim for and I usually hit my ratios right on the head. Air temperatures have been between the 60's and 80's. Temperatures here on Maui don't change much throughout the year.
But actually I forgot to mention this started before they were in the greenhouse. They were in pots in amended Pro-mix when they got it. Thanks for the input!
The promix could have been sitting in a damp warehouse. Before you bought it.
Id still check for calcium lockout though. Gypsum only gave me problems in coir. Promix's cation exchange capacity wouldnt be much different.
Good luck man.
Safe landing.
Tim