Are they root bound? Usually the rule is 1 gallon soil per month of grow to harvest time. So 5 gallons would be good for 8 weeks of veg 12 weeks of bloom. It's not good to disturb the root system if they have started to bloom. You could flip them back into veg for 18 hours of light re-pot them then a couple of weeks later flip them back. Never really heard of anyone doing this but it's possible in theory. Hope this helps.👍