Depending on # of rainbows & your level of objectivity, consider removing all rainbows before your holiday - remove to a separate bin with a sponge filter while you're away (how long is holiday?) or euthanize ...
Preventing other stock from consuming these dying/dead fish is strongly preferred - what other livestock are in tank?
If rainbows continue to pass at similar rate to these last two, will tank be overwhelmed with bioload???
I'd not buy any hobby grade UV - they won't provide any protection against mycobacterium (& very little else)
Re infection of other stock, disease progress is measured in months to years, so it's very difficult to assess infected state on companion fish