root bound questions and pot size 3 weeks into flower

just wondering if there are any ways to tell if your getting root bound ??? I have 5 healthy plants in 2 gallon containers. They were clones on veg for about 3 weeks and got 8 to 9 inches tall. Then i cut the lights to 12 hours. Now im at 3 weeks of flowering with nice little buds everywhere. They are know aprox 16 to 17 inches tall. Do you guys think the 2 gallons pots are fine and if not is it to late to go to 3 gallon pots... Also i did have to flush them because of minor nut burn... Water did seem to be draining pretty good

Do you have lots of roots starting to come out of the bottom drain holes?
Are your plants drinking up water (going dry) much faster than before?
Are you leaves drooping for no good reason (not over or under-watered)
Do they get nute burn with the same amount of nutrients as you used before?

Those are a few signs that your plant may be rootbound, based on my experience. Try gently popping out the rootball in your clones; if the roots are strung around the sides of the medium like a big ball of yarn, chances are you could be rootbound.

You really don't want to transplant in flowering unless it's an emergency, especially since the pot extra space will go unused as the plant focuses on making buds instead of roots. It could also make the plant go into shock and affect your results/yield. Since you're already in flowering, your plants aren't concentrating on building roots anymore, so you should be fine. Just keep an eye on 'em!

2 Gallon pots with a 3 week veg i really doubt ull get rootbound maybe 2 month veg would do that.