Well, with no diary to go off of.
I'm guessing these are autoflowers as well considering their size or did you flip to flower early on photoperiods? Either way, it looks like the plant never grew a good size root ball and didn't grow much before it started to flower. Small roots = Small plants = small buds. But this does look like a more extreme case since you say theres been almost 0 growth in 2 weeks. It could possibly be stunted from an early age. Very dark green leaves, so possibly of a toxicity stunting the growth. Too much nitrogen during the flowering stage. With little information this is what I have to offer. Thanks