Excellent post b'less! You answered most excellently. Disclaimer: I don't use coco - never have.
Did the leaf issues start after transplant or were they already evident in the potting soil?
If you feed with every watering, your mix sounds good for now. I don't use RapidStart but you probably could have gone a little heavier on it. I know you are treating this like pure hydro and with coco that's probably wise. Still, you seem a close to the low side on PH = very little room for error. It could explain the leaf problems, but dunno.
Did the leaf issues start after transplant or were they already evident in the potting soil?
If you feed with every watering, your mix sounds good for now. I don't use RapidStart but you probably could have gone a little heavier on it. I know you are treating this like pure hydro and with coco that's probably wise. Still, you seem a close to the low side on PH = very little room for error. It could explain the leaf problems, but dunno.