Skunk Haze- WTF

Hi, My skunk Haze clones are 1 month old and are starting to develope a red line down their main stalks.
Room never goes under 68.
Not sure if this is a gene thing?
Was feeding at 1/4 strength
2 days ago feed at 1/2 strength.
Yesterday, repotted them and today noticed the red lines!!!!!!!!!!!

Temps- day-80-83 night-69-73

Lights- MH 3ft away

Ph- 6.4-6.6

Medium-FFOF

Not sure wat to do at this point? :S5:

Nothing to worry about, I think its probably just a gene thing. If you notice the plants growing change or anything then it becomes a problem.