Purple stems and dark brown leaves

[Finlo420]

Just looking for more advice on these 4 clones I got a few weeks ago, I use biobizz grow 1ML/1L PH to 6.2 they have recently devolved darker stems and leaves and some of the new growth is starting to pale yellow, assuming some sort of deficiency but struggling to find out what, any help welcome.
I have 2 160w grow lights in a 3x3 tent

 

[BryanOconner]

Purple is usually from cold temps

 

[LoveGrowingIt]

When I see anthocyanin (i.e., the reddish-purple coloration), I think stress—possibly shock from the changes. More information about your growing environment would be helpful. There sure seems to be some nutrient deficiencies. Can you post a few pictures taken under white light?

 

[Choppr]

white/yellow margins indicate magnesium issue. I have used MegaCrop since 2017(jacks before that), and MegaCrop 2 Part since 2019 , I have never seen a nutrient deficiency using MC. Everything is in the A/B base formula, never need addl Cal/Mag either. Inexpensive robust Nutrient Blend.

 

[ArtfulCodger]

The first thing I'd do is dim your lights and/or move them higher. 320 watts of LED in 9 square feet is finishing intensity, and your clones' roots aren't keeping up.

 

[Finlo420]

When I see anthocyanin (i.e., the reddish-purple coloration), I think stress—possibly shock from the changes. More information about your growing environment would be helpful. There sure seems to be some nutrient deficiencies. Can you post a few pictures taken under white light?

What would you like To know about the growing environment? (Sorry bit of a novice) only my 3rd grown and first time from clones never had any real problems from seeds, here is a photo of each