Brown spots...

Hydro system( flood/ drain), hydroton pellets, 250w HPS set 20in. over plants on 18/6 light cycle, GH grow formula nutes at 1190 PPM fed every 2 hrs for 15 minutes, Im now into my 4th week or veg from seeds and I have developed brown spots on my lower fan leaves of 1 plant.. I have 6 going... whats causing this.. Ive read N def, Ma def, but whats really going on...oh there are no bugs or gnats...see photos... MX

Have you checked the PH recently? Could be something simple like that. Also look on the underside for bugs

FattyCaps

looks like a Mg deficiency

Ya just checked it.. PH 8.3+..........Im off to get PH down.....then go from there.. they water in 20 minutes....