Dieing lower leaves,not really yellow

Hi there, I got a couple ak's in my veg room that have leaves slowly dieing from the bottom up, I've already tried transplanting and feeding with cal/mag/iron/si, and feed with nitrogen. feed and water always at 6.3ph water, using happy frog under a 400w mh ,at the moment for base nutrients I use jungle juice micro and grow

how far above them do you have the light?

they don't look like theyre getting as much as 400watts or there just very stretchy

don't see anything much in those pics