Deficits

It can be phosphorus, potassium, nitrogen, molybdenum, etc. Imbalance or genetic bias. It's more likely to be phosphorus related if not genetic, but it's always more than one factor, just some factors more dominant. If the reddening plant isn't the banana blaze, I recommend you use a bit more calcium than in calmag, perhaps citric acid, a bit of trace mineral stuff, potassium, carbs. I also notice the "yellowing" is at he tops, so it might be light related too, coz it doesn't really look like nitrogen itself. Unfortunately it's difficult for me to say, because I don't know your (or those plants) or the nutrient and soil balance. So I'm basically just speculating.