Purple Stems, something to worry about?

I started a new run with 5 plants (4 Green Crack and 1 Bubba Kush Pre 98.

They are all running House and Garden Nutes under a 1000 watt hortilux in a Radiant 6 hood.

At week 2 the GCs started to go yellow, then by the end of week two, 2 of the GC plant main stems were completely purple. The other 2 GCs are starting to go purple as well, just not nearly as bad.

I put the two back into veg and it seems the purple is slowly fading.

Meanwhile the BK show no issues.

So what am I doing wrong to kill the GC and cause the purple stems?

Why is the BK still happy?

Some purple on a plant appears to be normal, if there is deformation of the new growth, then a secondary deficiency is indicated, Ca or P, if the growth appears normal ( but slower ) and the leaves are a pale green or yellowing, then its most likely a N deficiency. Over-lighting occurs rarely, but uses up more N than a standard strength nutrient solution. Check the strength of your N application, or the pH. Be careful, one good dose of nitrogen will turn them a dark green in a couple days, one over dose of nitrogen will be the end of your plants.

purpling stems is from genetics or being cold i dont think it has to do with nutes