Pale lower leaves turning yellow

[Steverlin]

4 week old plants, 125 W LEDs@26", 5 nodes, in Moss&Coir with worn casings, bone&blood meal, feather meal, forest products and perlite. PH 5.8
one of three plants in 6"diameter x5" deep well drained pots with 1" layer of washed volcanic rock in bottom is developing a bleached light green color with lowest set of leaves turning yellow. One of the other two is showing lightening lower leaves too. I'm at a loss. NONE of these symtoms appear in all I've been reading. Maybe long term slightly over lighted
(lights a bit to close) or nute burn???

 

[4barrel]

well if it's the lower leaves turning yellow, it's not light burn cuz top ones would burn first.
for hydro, your PH is right I think
being that it's the bottom ones it could be nitrogen def.
some pics would help

 

[oldjarhead100]

think 4barrel is correct sound like a nute problem . try just a little n in your next watering