please help me someone.

they shouldnt be root bound in a 3 gallon tub at 18 days,

Day 18 of bloom, I assume? The root system has done most of its growing at this point, but if you feel like they're root bound, transplanting won't hurt. Just be gentle with the roots (as always).

More soil is pretty much always better.

oh if its day 18 of bloom,i could see it possibly,thats about time i put mine in 5gs

Yeah... Bloom.

did you pull it out of the pot to see how roots looked? and how tall or bushy is it,do you have pic