Raspberry Cough Nutrient Problem

First grow, indoors in soil. Emerald Triangle 420 Soil in smart pots, under LED lights.
Having a nutrient burn problem, at least I think that's what it is. The new growth leaves have yellow tips, and some of the lower leaves have yellow spots. I flushed the girls with plain RO water today to try to correct it.
I have been feeding them every other watering with 500ppm GH General Organics Series and molasses for beneficial microbe growth. The plants are exactly 4 weeks old today.
Any advice on the issue? If it isn't nutrient burn what else could it be?

you're feeding to often, especially if you have a soil that has nutrients already. you don't have to feed so much. hard to say how often to feed but it's obvious you are feeding to much with those burned leaf tips.