It's usually a defidiency of some kind. Just up the veg nutes. Put those clones in soil.
In my expierience cold causes pink leaves/pistils, but purple stems isn't from cold. Some lines can be genetic but if all the stem is purple, probably def.
I really think it is just the strain. Maybe a deficiency on P or K but I wouldn't worry yet let them grom longer till you give yourself a panic attack. But when it comes to nutrients less is better than too much.
it is not the strain, ive done this this strain many times and its a 2 hybrid clon. it is also in hydro system, so can not put in soil i guess i better just gonne keep ph in the glass at 5,8 and a couple of drops of A & B Leaves in.and see what happens. my only worry is that the outcome of the plant will surfer....
purple stems can mean......................genetically normal trait, stress, cold. purple stems by themselves mean nothing. with leaf symptoms, that can be a different story.