Recurring RI in Retics During Winter

[PsychoSnake]

Hi guys, long time no post. (Like years. Life has been... Chaotic...)

Anyway, I was wondering if anyone had any ideas on how to combat this recurring RI that my two retics typically get during the winter months every year.

The Environment

They both live in large Vision Cages with ceramic heat emitters for their hot spot (90F). The ambient temperature of the room ranges from 80-82F. (When the retics are ill the temperature is bumped to 85F.) room was custom made for my snakes so the room is heated by a water based radiant floor. This means there are no drafts, it is naturally more humid than an ordinary room in a house but it is slow to change temperatures on demand. An increase in temperature from the thermostat may not take effect until 24 hours have passed I've learned as the heated pipes are under 6 inches of cement. But I have also installed a wall mounted electric heater to quickly heat the room when needed. The room also has a denser type of insulation than typically used for a home. Additionally, despite the above measures I've taken above to climatize their room I notice extreme weather during winter does have a negative impact on the environment even if subtle. E.g. a slight drop in temperature.

What the Vet Says

My exotics vet believes what these two tend to get is actually a viral infection that they carry always, and it only appears when a stress threshold has been met. He usually prescribes Fortaz injections every 3 days with oral Baytril (injected in a F/T rat) every other day to prevent complications for 6 weeks or more. I've gotten so good at treating RI in my retics that my vet just discusses and asks me over the phone of what I need since I can examine them too.

Oddly only the retics have this issue. In this same room I have 9 other species of snakes. It is rare for them to be ill.

What am I doing wrong?

I must be overlooking something, because if my vet is right then they shouldn't be getting RI if they are not stressed.

The medications are expensive and it's not fun for my retics. It takes a long time for them to stop associating my touch with giving them a shot. Any ideas would be greatly appreciated.