So sorry :( Unfortunately I don't know what it could be, but I would take one in to the vet to get a possible culture or something done to see what it is. Cultures don't generally cost that much ($15 at my vet) so it might be worth it. Good luck!

any skin sores/pimples/lesions at all? mice are very susceptible to herpervirus too, and this can sometimes be paired with eye boogers.

No topical lesions of any kind, just all that other weird stuff. :(

no way of knowing for sure unless you get a culture done. sounds viral, whatever it is.

have you recently changed their food? or are they used to getting extra "supplements" like fresh veggies when you are home, that they didn't get when you were away?  When I bred my own rodents, I tried changing food at one point - actually increasing the quality of the food.  I thought I did the transition slow enough, as my vet recommended.  As soon as I made the final transition, I had mass cannabilism occur. 

That's all I have to offer, other than that, I'm sorry for the loss in food and lives :(

I think it sounds viral too. It's strange that only the feeder mice have succombed to the disease, I've noticed. My good hearty breeders are thriving and I have a few litters. I haven't changed anything about their diet, same Rodent Lab Diet 5100. The watering system works great too. This is just driving me nuts. Now my "live" eaters aren't going to get to eat until my stock is replenished. I'm thinking about hitting the local reptile show and getting some new breeding stock. I'm devastated over this whole thing. I've put so much time, money and effort into growing my colony and THIS has to happen. My other CVT friend thinks it my be paramyxo. I don't know what else it could be, and honestly, I just don't have enough $$$ to take a mouse to the vet to get cultured right now cuz I spent everything on Christmas presents, lol! Anyone else ever have anything like this?

I had something like that happen to a bunch of mine last summer. I figured it was because they got sprayed with wasp spray by accident, but the kept crapping out with some kind of virus. I culled/discarded everyone, bleached and started again.

Several things occur to me. The new rack had some sort of residue and it poisoned them. They were contaminated by either a wild rodent or one that escaped and contracted something. They ran out of food/water and got cold. No matter what it was I recommend following gfx's advice. Freeze them all, bleach EVERYTHING and start over.

Was it all in one tray? As a breeder i would say the water system sould be cleaned and checked, and the trays.

Cryptosporidiosis?

...from experience i have to ask the obvious...are all the water spouts working? 

I kind of have to go along with Jen and ask, could they have been with out water. It sounds like typical behavior with mice who have chewed through their water bottle or had clogged nipples. Especially the hunchback part.

I have to concur--a clogged water valve is probably the cause.  The cannibalism is the big tip-off.

It's a brand new system and I went through each and every spout and made sure the water was working before I left for Boston on the 2nd. They were all still working when I came home. That was the first thing that I thought too, but they all work. What about a drop in temperature? They have been moved down to our finished basement and the temp is a bit cooler.

Hm.  I had some mice come in with similar symptoms once.  I lost most of them, but the survivors went on to recover and breed.  If it's the same thing, then the solution is to disinfect the bins that are affected, and quarantine all the rodents showing symptoms separately from those that are not (or euthanize the ones that are sick).  A drop in temperatures might have kicked their immune systems down.  It might even be mycoplasma, which all domestic rodents carry.  Do they have sniffles as well as reddened eyes?

A third thought--did the rodents you put into the racks have experience using valve sippers for water?  They do have to learn it, so they can teach their offspring.  When I first put rodents from pet stores into my racks, I showed them the water several times, and kept a normal water bottle set up next to the sipper valve until I was sure they all figured it out.

Hi WWP (hehe), I didn't notice any reddened eyes, just a lot of crusting around them, like dried up tears. I'm not sure what sniffles looks like in rodents tho. All of my breeders are robust and healthy and are still breeding. The feeders that I seperated out might not have know how to use the water system, that is a good thought. I figured that it would just be a natural enrichment process trying to figure it out. The feeders were pretty young but still would've been considered adults. Those were the ones that kicked the bucket. I did quarantine the sick ones and bleach all the racks that the dead ones were found in, and all the quarantined ones ended up dying last week. I'm hoping that I don't find anymore dead ones tomorrow when I clean the cages. :|

Well, it looks like whatever it was has run its course. No dead mice for a while now. Here's hoping for the best!