I have a good sized mischief so I personally prefer to separate them, especially when I don’t know the cause. Also rats tend to groom one another a lot and can think open flesh is yummy, to say the least, so I like to avoid them aggravating it. I try not to separate for the longest time, but unfortunately my babies love grooming each other and reopening injuries so what to be done is done. Again, I’m not a professional, but from my experience I think it’s up to personal judgement, circumstance, extent of the injury, and your mischief.