Red stem ???

Five weeks old and she is starting to get a red stem. I googled it and ppl say it's the nutes ? I'm using ionic grow I feed once every two weeks and water every three days. They in a 50/50 mix of compost and coco (experimental) the reg plant is about 2foot tall but the feminized plant is only about half a foot tall. It's the big plant that's the most red. I'm not too concerned because other than that they lookin healthy and the big one is preflowerin. Any words of wisdom ?

It could be magnesium. If the top leaves are curling up "tacoed" than I would suspect mag. Get some epsome salt and mix one teaspoon per gal of water. I have found mag deficiency is common when using ro water. I put a pinch of epsome in every watering, and my girls love it.

Also, coco is known to lock up calcium, so a Cal mag might help

It's a sign of stress..... old stress. At some stage you stressed your girls and the red stemms are battle scars. Don't worry about it, nothing you can do now other than think back to what you may have done.

Feed some CaMg with your waterings.

could be a purple pheno my stems on my plants turn purple/ red befor the leaves do!

you water every three days........
water by weight of pot......not on a timed schedule.

Could be a few things,If they are looking healthy at this point,I wouldn't worry to much.