It's minus 30 today, I'm staying close to the wood stove.
Hope it's warmer where your shoveling.
You just revealed the uptake problem with your girls.
Besides the cold concrete.
Promix is a peat based media with perlite for aeration.
Pro mix is therefore hydroponic and requires a ph of 5.8.
I ran promix for a year before switching to coco.
I kept the pots wet.
Fed full strength G.H. trio to runoff at 5.8 every day.
I have since that first year talked to many people using promix.
Overwhelming majority give plain water every other day feed / water / f / w / f / w / f.......
full strength nutrients at 5.8 ph.
All at 5.8 to run off every day.
You have a buildup in your root zone from no run off.
I would run 3 x pot size plain water though the pot.
Then feed at 5.8 ph .
Then going forward chose one of the above feed schedules.
I found bokashi & frass helpful in the pots aswell.
That's a lot to process sorry.
Let me know what you think.
Hope everything is going good.
#VIVOSUN #Love What You Grow
Bill284