ph'ing is pretty important, imo. i don't believe in "root-bound," plants. as long as all needs are met, they do fine. but, if you're planning on transplanting, it's ready.
I would never transplant an autoflower they dont respond very well. they are time limited so if it starts growing new roots it will slow the budding. never transplant or top autos they usually get stunted if you transplant if you top you get all popcorn. up the nitrogen a little. imo a 2or3 gallon pot is perfect for autos 2 gallon works great in most cases.when you get over three gallons they dont do well either. I think your looking ok it actually helps to let autos go a little rootbound
u need to flood that gurl with proper nute water mixture mix up a gallon and slowley apply it . put it into another pot so the run off cant roll out right away like about 15 mins . simular to watering from bottom up or actually mix up 2-3 gallons and feed it from bottom up so u can soak the root zone .
I'm betting you have a nutrient lookout caused by ph imbalance. That said, until you flush the soil with ph'ed water to rebalance the root zone; Adding more fertilizers at this time will only worsen your problem. I had this same problem on my first grow while I was waiting for my ph pen to arrive. Also, you can buy a very cheap meter that you insert into your medium and it instantly tells the ph of the root zone.