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.

Sounds like you're doing everything right! Dont transplant, youre too far into flower and if its a 3 ft plant in a 3 gallon bucket you're good bro! Happy harvest soon