Hey bro garden is looking good, i think there are some real good points here and most are from yourself, the trouble with potting up to a bucket that size is that the medium that surrounds your girls roots is wet so your roots are not searching for water, there will be some roots that make it to the edge fast but that will not be enough to dry up them pots fast enough for your girls to be happy, Ideally you want to pot up in anything that is to much bigger than what your girls are in, you want them to fully root out there container than move them up a size fully root out that container and move them up a size this will give them a huge, strong root ball able to take most disease and pest thrown at them.
I run a wet dry cycle meaning i will never water my girls in till there pots are dry and light and in soil i wait till i start to see first signs of wilt (can be dangerous but it get get it dialed in you'll be amazed at the results) i then fully water them leaving them to sit in the run off for 10 mins if they have sucked up all the water i water again in till i see run off, once there is still water left in the tray after 10 mins i put here back in the grow room and don't water again in till pots are dry, cannabis plant love there feet to be on the dryer side of the scale.
With your cold temps at night it is crucial to raise them to ensure all nutrients needed are absorbed, especially with a pot that size the surrounding wet medium with become very cold and the roots will not stretch and growth will be stunted by to much stress. I had a similar problem with my second soil grow i diagnosed every deficiency under the sun and tried to treat the problem, the trouble is i had no knowledge and missed the first rule, if she has everything in her pot why is this happening ?? Simple environment... i placed a heated blanket under her pot and within 2 weeks she was a different girl i was absolutely AMAZED!
First lesson learned that's it i was hooked!
Re potting as another option and will get your girls back to optimum health the quickest.
Sorry i just been waffling on there brother not sure if any of that made sense haha Well hope you there is some thing help full out of it!
Good luck mate