The big problem of Q in a rack is somethings like mites travel and walk about it is possible to spread exoparasites by proximity and also air born nastys as well.
Ideally, isolation is needed as much space as you can muster. I keep the Q tub in the same room but use a tray under it filled with diatomaceous earth to kill any exoparasites that escape the tub. I also use totally separate tools ect and do not ever touch anything from isolation to the rest of the collection.
Testing is not a bad idea I always do a fecal test and have started having IBD test as well just in case.