The stems began to turn red

check the root temp during the night, at least 21c is good.

I wouldn't jump into action on anything just yet. Sometimes stem coloration can point to a deficiency but you can also see coloration from LED lighting, they tend to bring colors out in plants. I usually don't stress stuff unless the growth of the plant seems affected. Since you're growing in coco I would incorporate some CalMag into your feeding if you're not already. Might help with your wavy leaves a little and prevent future headaches.