I would say they probably are root bound as you say because they are only in 2.5 gallon buckets. Well, 2 of them are and the 3rd is in a pot of about 2 gallons.

There is no light leak though, I can be positive of that because where they are located gets zero light during the day and the only light is what i provide.

I would guess the humidity is kind of high. I will take steps to reduce and will get on the anti-fungal.

Thank you very much for your help!