Promix is peat.
Never heard of the HP; it's the BX that cannabis growers use, so I looked it up... seems it's pre-ferted as well... 'micronutrients and macronutrients' are listed as components. pH range is listed from 5.5-6.5. That's quite a window... yikes.
You gotta get them into better medium.
That is only going to get worse.
http://www.hort.purdue.edu/hort/faci...s/proMixHP.pdf
I hate peat...
Flush with water at 7.5-8.0. Find a new soil. Repot at your earliest convenience.