I agree plants grown under led get more calcium or magnesium problems, but then there is quite a big difference in the feeding times. If say 2ml cal mag was added to a hps grow, which takes 3 days for the soil to dry, then how would 2ml cal mag work in soil under an led grow, that takes 6 days to dry?
Last grow I used cmh only and didn't use cal mag once. I have recently added led. I used to epsom salts leaf spray feeds when I grew under led before. May take that up again.
I think with led, it's much easier to overwater. You just don't have the heat that will help offload extra water, like hps does.
Also many led growers use their leds way too close, which in turn makes the leaves dry up and go crispy. Then they blame calcium or magnesium
In the summer I'm going to do a few tents with 100% led. But not 50w per sq ft, more like 20w. If you need 50w per sq ft of hps which is what 8%-13% useable light, then 20w per sq ft of complete targeted par light is more than ample.
On the note of the plant drying out slower. I used to feed auto's at 8ml per 1 liter, which is double the strength of the maximum shown on the bottle. Some of the best plants I ever grew!
Try it on one of your led plants with double the nutes! Not in veg though, you will risk nitrogen toxicity. In bloom the plant just takes what it wants with regards to organic bloom, not synthetic bloom.
Just feed double strength, but the key to this working is getting run off. You must wash all the crap out from the last feed or you will get problems!
I grew some seriously fat buds on double strength bloom feeds. I think the plants are less likely to suffer a deficiency that way.