Small and slow

I’m not sure if it’s just impatience or what, my name is Gabriel and I have 3 pretty plants that I grew from Mexican brick weed. This is 2nd time and I do know for a fact good smoke can be produced no matter what strain.
So one plant is really taking her time in flower, I’m thinking she’s really close to 4 weeks. Lots of pistols at the bud sites. They are just small to me and not growing. No more fan leaves or growth so I’m thinking she’s stopped her vertical. The buds are about twice the size of a thumb for top colas. The bottom stuff if big knuckle size. All leaves are green but the pistols are starting, very little, to turn pink/tan. I feed with agrothrive. 2 spider farmer 600s indoor 2x6 space. No signs of anything but slow to swell!! Help, will they fill out? Should I start a bloom booster?

When is the last time you transplanted and what size container is it in? Adding more nutes does not make plants grow bigger or faster. Adding more wattage does.

off topic, but your going to be in for a surprize come harvest, me and a friend grew out some mexican brick weed years ago. and it was better then the original weed. probably due to all the goodness going into but and not seed production. soaring high, realy energetic lovely sativa weed

They were transplanted into 5!gallon cheap pots. Good soil mixed with about an 8th of ceramic balls for experiment and it’s worked so far since transplant. I do have my lights 16 inches away. They call for 12 maybe that’s where the issue is!