They look good although, yes, you’d like them to be a little bigger. But they are vegging and have not triggered yet. There can be numerous reasons other than LST for slow growth… Over/under watering, insufficient light, soil too hot, RH and Temp, air exchange/ circulation, etc. And one of the biggest is GENETICS… Autoflowers can still be hit or miss.
The good news is yours show no signs of nutrient burn and if anything may need a little more water. Small pots will dry up quick… Also the roots will be down the the bottom quick so maybe give the containers a bottom water to not let the feeder roots get too saturated higher up.
At this point, I would want to see them at about 400-600 par depending on strain.
For example… my current autos of similar age. I have grown hundreds upon hundreds of autos so experience does help.
Pineapple runtz auto at 15 days
Beary White auto at 20 days
Little better perspective for size
You can see the only LST these plants are receiving is some “leaf tucking”.
by end of week 4 to week 5 they should have progressed to about this (below pic)… If not, I would question the genetics knowing the environment and containers are dialed.
Also keep in mind a lot of strains like double grape or the pineapple runtz may stay a bit squat until they hit pre flower around day 25-35 and then stretch the satelites big.