Mice probs...

[Zoe]

I'm having problem with my mice. The problem is they keep bloody dying on me.
This has happened twice, with two different colonies (granted, they were from the same store.) In both cases, the mice arrived, apparently healthy. Not long after (a week or two) the male got very sick and was 'put down'. Rigor mortis set in minutes later. WIth the first colony, I thought that the females were killing the male so I killed them all and got a new colony. Now, the male died (a couple weeks after I got him) and just recently a female died. Now the other 4 females look bit... squinty, just sitting in a corner not really reacting (they do run away when I put my hand in), their noses to the ground.

Not sure what's going on... any ideas/suggestions?

Thanks!
Zoe