I agree w/ the guys-- also gotta ask a few things....
1) What kind of soil is that? It should not seem that compacted when dry...
2) How are you watering and how often?
3) What are you feeding them?
4) 12/12- now-- really? What strain is it? Not all can go 12/12 that small and be worth the effort...
Make sure they are saturated completely with some drainage out the bottom both when you feed AND when you water- then no water/nutes until the top 2 inches are dry and the planter feels light... IMO- transplant into slightly larger planters with a fluffier soil mix (promix, light warrior etc..)
Be sure you feed them only 1x a week- unless the soil has it's own N-P-K then do not feed until they've been in the soil 4-5 weeks... then start at 1/4 rate and work up...
Follow a feeding chart for the nutes you use-
Always add a micro-nutrient even if your nutes schedule doesn't call for it-- every other feed at 1/2 rate... never hurts (CalMag/Microblast etc..)
If that is a 100% Sativa from seed not clone- go ahead and grow it in 12/12- it keeps them manageable- BUT they have to be in a planter based on the finished size of the plant- not the current size- and if it is a clone, it will not get as much height/growth this way as the seed plant will since it is already an older plant and will start to bloom faster...
If it is a 50/50 or Indica dominant- go back to veg a while longer--
Either way- IMO- even though she's presexed, she's not full-bloom... put her back into Veg until you have her healthy.... Then she'll really preform better for ya!