I've been putting off on asking this here long enough. Last fall I started noticing small-medium sized nymphs dead under the pine bark I had in the unnamed tank. Then I started finding them in all other places, even after I took the bark out recently. Today I found a decent sized nymph dead in my other tank, along with even more dead ones in the unnamed tank.

What's weird is I had the bark in for about a year before anything unusual started happening. And for the most part whatever's killing them has mainly killed small-medium nymphs in the unnamed tank (which is closer to the window).

When I find them they are perfectly intact, sometimes they're even still a bit twitchy. Could it be some kind of toxic mold? Or nematodes? Maybe it's just a bit too chilly?

I feel guilty I haven't asked here sooner. I've lost at least 50 nymphs so far and I feel like maybe it's something I might have done I need to pay more attention to them....

Might be either temperature or humidity problems. Most likely humidity.

Hmmm, I mist at least once a day. Then again, winter is pretty dry. How many times should I mist them to keep them healthy?

I am going to change the substrate soon too.

If you are having problems keeping humidity in, I would just put in a small water dish with some pebbles in it (you don't want to drown anyone). Since they are by the window, it might be letting sun in and depending on the cage it could cause a rapid increase of heat during the day that you may not be able to see if you are checking the temp in the morning or at night.

A picture of the setup would be tremendously helpful for you if you could post one....

Okay, I've been watering them a bit more than I used to and so far, I've only found one dead (on a day I was away too). I hope it was just humidity, seems like that was it so far.

I thought Pine was toxic to most insects?

I've heard that, but it didn't seem to hurt them, at least not until a year after I put it in.