Ignore this^^ it DOES need transplating to a bigger pot first and formost. You can't tear the root ball all to hell, but when they are that root bound, Slayer is right,loosen em' up some when do it, you don't have to be that careful with em' ..it's a weed. Once you get it potted up, feed some balanced fert with some nitro and some bloom nutes as well. Look for a 5-10-5 or somethin like that with a little more phospkorous for flowering, but with some nitro too.Looks to me like its just normal yellowing of fan leaves due to the start of flowering. Transplant might help a little if.... You are careful and dont hurt it when you do it. Gentle gentle gentle. I wouldnt be concerned with the yellowing. Good luck. What strain?
^^^ This ^^^i disagree id be concerned with the yellowing it shouldnt be that yellow until its towards the end of flowering. it needs something for sure the 5 gallon bucket will help for sure and id give it a high nitrogen nutrient if you got any. when you transplant your roots are most likely root bound and will be all coiled up in bottom of pot, be sure to pull them apart a little bit and ruff the outer edges of the dirt up it will help its roots take into the bigger container.