Purple Stems?

So i've been reading through my Medical Grower's Bible and can't figure this out. My cheese plant's stems and have all turned purple and the lowest, oldest leaves are yellowing. I have read this can be because of nitrogen or phosphorus deficiency. I have added nutes and nothings changed.

Today is their first day of flowering.

Previously they started on 24, and after a week i eased into 18-6 over a time period of about a week. I left them in 18-6 for a week than slowly eased into flowering.

I am giving it 1/4 of the recommended dose of flora gro and flora bloom nutes.

They are under six flourescents. I can figure out the amount of lumens if that might somehow effect it.

Temps High/Low: 88.8 F/65.4 F

Humidity High/Low: 44%/10%

Anyone no other reason stems may turn purple? I have looked around this site and all i have found is its either the strain or a deficiency of nitrogen or phosphorus.

I have a feeling my anwser is in the following grow journal: https://www.rollitup.org/grow-journals/125765-cheese-whole-cheese-nothing-but.html

But my browser cant seem to open that page.

i don't know a whole lot about cheese strains, but is it possible that the purple stem is part of its genetics? I've seen pictures of perfectly healthy cheese strains and their stem color was almost identical to your picture...I could be wrong, but I feel like if the stem discoloration was a problem, all of the leaves that were on those stems would also exhibit some sign of stress and IMO (from what i can see), the majority of your leaves look pretty healthy