Does this look normal? Purple areas on stem appearing on multiple plants. Day 22 flower

Purple in stems can be 1) a sign of needing to add some calmag (calcium deficiency although your foliage isn't looking like it has a cal mag deficiency), 2) temperature fluctuations (this is somewhat normal if your temps fluctuate often from cold to warm), 3) Genetics. If you are sure its not a cal mag deficiency or genetics, I would try to just make sure temps are not dropping drastically.