I've never done a run with Pro mix. I know it's a popular base. I'll probably try it one day.
I use FFOF, FFHF, Coco Loco, Perlite, Rice hulls, Worm castings, some Good Earth general purpose organic ferts with a few TBSPs of dolomite lime and some bio-char. BUT....on this last run I started out without the lime and bio-char and the mix turned out to be VERY acidic. I got ALL kinds of lockout. So, I ended up flushing/leaching the pots with pH'd water until I got the runoff to be in an acceptable range. After doing all that leaching, the "soil" basically became inert -as in a drain-to-waste hydro kind of thing....looks like soil, but has nothing left in it. So, I started a Jack's 3-2-1 regime and, after about a month setback and looking terrible, the plants are back and seem stronger than ever. I really believe that a lot (if not most) of the deficiency problems comes from an underlying pH problem -at least for certain types of mediums like potting soil mixes and stuff like that.
General Hydroponics pH test kit (with the green liquid drops) is now my new best friend!

Good luck! I hope you solve your problem!