4 Strains, 2x4, LED grow

hey guys, thought I do a little Diary. since I am already on the 23rd day of flowering, here some words of what happened so far:) I am growing for some time now.. It is my first grow since 2 years, but I did some. only HPS, soil, coco, hydro, DWC.. sog, scrog, etc. my max yield was about 750g in a 4x4 600W HPS. I started small again. 2x4 tent, 400W Lm301H's, I build one big lamp with 4x 120W lm301h's, and 8x 660nm epistars per board, running on full power right now (390W approx).. Had them on low power for a while, about 200 watts or less, but closer to the canopy, in fear of lightburn, then I put the lights further up, upped power to 250W approx, and they seemed to do better. I think since I put the lights on 100% they are doing again a bit better, and I now raised the lamp to 50cm, somehow It looks like the plants need that intensity from the lamp. I've read that transpiration issues do make weird problems under LED. I upped the nutes also last feeding, 3/4 dose last watering. These 4 strains, 13 plants had a rough time in the beginning, caused by .08 EC water which locked out some nutrients, so the veg took longer. since flushing, they bounced Back, this should be a selection grow, from seed, so I took clones for each plant, and another prune about one week before switching to 12/12, after the nutes were dialed in and everything. these are the motherplants flowering. Then in week 2 I finally added a net above the canopy,(in fear of them shooting up lol), repositioned the plants and cut some dying lower branches too. lots of lower leafes were falling off during stretch, so I added more N, and also I guess not enough phosphorus, so I added a bit more P to the mix. but still the upper growth looks kind of very light green or yellowish.. idk if thats light burn, or not enough nutes.. I feed very lightly every 2nd to third watering, dosage about half of what is recommended in soil. last watering I did with only epsom salts in case of sulfur deficiency, ( the yellowish upper leafes could indicate that)... last feeding was 3/4 strenght nutes NPK about 13/16/20. calmag usually 1ml/l every watering... I use RO water now. a little help with diagnosing is highly appreciated! especially for the yellowing.. I don't think it is light burn. lamps 50cm away, and since Iam pulling 100% from the lamp and give a little more nutes, they seem to do a bit better..:)