unfortunately, you are going to need to write us a novel as to EVERYTHING that has to do with your set up. Where do you keep your snakes, how do you heat them, what snakes are sick, the ones on the bottom, middle, top, windows in the room in relation to where your racks are.ect..ect..ect. EVERYTHING, and then people will be able to give educated advice on problem solving for your issue.
I experienced/am experiencing the same thing you are. I have a second story bedroom dedicated to my ball pythons. I have rearranged the room 3 times, bought different products for different reasons. My bottom tub ALWAYS gets a URI this time
of year. I have covered vents, gone through a couple t-stats on my way to learning that 1500w is a $#!T load of power and ruins t-stats. I am now getting a Johnson Controls finally. I have built a better rack than my last, and am now going to just
buy a few Rhino Raxx. I have dumped baytril into at least 10 different snakes over the past 10 years. I am now going to tint the bedroom window AND cover it with plastic for the winter, so Tint, plastic, new racks, new t-stat, box fan, oil heater, I
think I am slowly figuring out the algorithm for an artificial African environment, now if I can just get the humidity to stabilize that would be great. For that, i am going to insulate the entire room with that silver rolled up insulation stuff.
I still do not know where 2 gallons of water are going in a 24 hour period..lol.
The hygo says 65-70% with 2!!! humidifiers going in the morning, and when I come home, they are depleted and the hygro reads 35% humidity in the room....WTF!!!...haha....um....I don't think I am going to drink Monster Bombs and reply on Kingsnake forums anymore..lol. Next time I might write a whole book.
Good luck with this. I know that it is a very depressing part of this hobby.