lower canopy suffering...will it spread?

im growing 3 sativas and 3 indicas all clones from the med center. the thing is all 6 are showing lower leaf death and some yellowing of the lower shoots. the buds on all 6 of my plants are healthy and growing nice even though my closet space is 2 ft x 4 ft and about 7 feet tall. the sativas are 4 feet tall and the others are about 3 ft tall. heres some pics 1 of a bubba kush plant and the others are the snowcap. and i have all my plants in 3 gallon containers. maby its signs of being a rootbound plant. if they are, and they have exactly 30 days to go, is there a way to take care of them so they'll grow healthy?

2 pics are bubba kush and the last one is snowcap. all 3 look like that.

whats the PH level for the soil. the way the leafs are shrinking and curling under like that almost looks like when they arnt getting the vitamins they need. i would start by checking the ph lvl for the soil. if its too acidic the plants will have problems getting the stuff they need. if it is , just give the soil a good wash threw by pooring several gallons of water threw the soil. give just water for afew days after that and see if they start to comp back before ya add more fertalizer. Good luck