How much yellow is ok when flowering? Amongst that, my top stem is turning white.

I recently switched my soil to MANA, I got some AK47, Aurora and Candy Kush. I have been putting Hygrozyme in with every watering for few weeks because I had no root development (I think due to root rot), the tips of my leaves were curling up big time. After the Hygrozyme and soil change they have gotten better, I am getting tons of roots, the tips are still curling up a little bit. But it's not causing as much problems now...besides, I am not sure what else to do. It is not heat. I keep it at 85 degrees steady. Anyway, new problem... the plants are yellowing more than usually and I have also noticed some purple stems (I think it might just be the type of plant) and the top stems on some plants is turning very light, almost white. So how much yellowing in flowering is normal? What about the light stems at the tops? Any suggestions with the tip leaves curling up? I added some pictures of fan leaves turning yellow. I appreciate any help and experience. Oh I have put some kelp meal on top of the soil...someone suggested that. I am not sure if they are getting enough nutes.

In flower the fan leaves will yellow, starting at the bottom working there way up the plant. That's normal to happen.
Did you cut all the bad Roots off the plant before you transplanted?
What your talking about sounds Phosphorus and magnesium deficiency. Or soil PH might be locking it out. or It might just be a straight up deficiency.
She might even need some Nitrogen.
Some plants have purple in the genetics. It sounds like yours is sick.