@dirty.
i think its calcium deficiency. check this page out over at ICMAG > http://www.icmag.com/ic/showthread.php?t=11688 -- scroll down to Ca section - maybe check them all out.
what nutrient solutions are you using. doesnt look like light burn at all to me. you're only giving them have power nutes every 5th day? i dont know, but personally that doesnt sound like enough. again, what nute lineup?
dirty,
i dont like using lime in indoor grows...i feel its more suited for outdoor growing where pH is more likly to fluxuate, indoors usually people check their pH before water or feeding, my personal thoughts..but i would say your soil is getting lockedout and a nice solid flush followed by a good feed should help...also dont know about the medium your using, i strictly use FoxFarm..good luck bro
EDIT: also i bring my pH up to 6.7-6.9 before i feed or water
I flushed it last night. When should I feed?