purple power 4 weeks flowering can i transplant

i been flowering 4 weeks growth seems to be slowing down or i look at it to much but i got the plants in like a 3 gallon pots its two purple power plants should i finish flowering in the pots or transplant to a big bucket because the roots are starting to come out the bottom & the plant is almost 3 feet tall please help the plant is in verry good condition & i want a nice yield should i just be patient by the way the plant is mostly sativa & im using a 600w hps about 15in from light with a air conditioner cooling the bulb keeping the temp down between 75 & 80 at the tops here are some pics tell me what you think. is it to late in flowering to transplant.

I wouldn't transplant this far into flower, you might shock the plants by damaging the root system. I would just go with the way it is, try and cover the roots up with something if you can to keep the light off of them.