plant error?

ok not sure why this happens but the stems on both my northern lights and purple kush plants have like dark purple vertical strips or veins on them and on the northern lights is almost black colored veins/strips any ideas ppl, it seemed to happen at the cloning stage while roots where still being developed but there 3 week out of cloning and big healthy bushy plants no signs of nute stress ect.. i cant figure this one out any comments or solution would be much apreseated ty PKNL.

As long as they're healthy thats all that matters....Its winter time....Colder temps can make stems go purple like that.

I grew a few strains over the summer/fall....all stems green....this grow....some have purple stems....but my grow spot can get to 68f at night....cold temps.

Genetics can also play a part.

purple kush its totally normal to have purple stems but not sure about northerlights though. Peace

thanx for the input guys not to worried about the purple kush haveing purple stem just weird the northern lights has it to

ok ive noticed the discoloration starts while the clones are in the clone box taking root and now my NL plant is like 4 weeks out of clone stage and is growing about 1" everyday nice and healthy the new growth is a bright almost neon green and the strips just seem to fallow it up as it grows the temp is 70%f bee useing plan water and floros on it so i couldnt say whats causeing this little abnormality