The stems began to turn red

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

The coco feed from them should be all it needs if its well rounded. I can not find the NPK breakdown with the micros of that brand, When I looked at their website it does not have them listed either, I find that sketchy when they don't have this information available on the product page. So look on your bottles and confirm it has Micros and Macros, NPK CaMgS exct. If not, then it needs that. Red stems is sometimes related to Mg or P but I doubt that is the case, remember to get a good amount of runoff with each water to prevent buildup. Good Luck!

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.