Project Monarch Health
The only thing that I can recommend is that you thoroughly sterilze your containers and make sure you rinse them thoroughly, too. Bleach residue is not good for caterpillars. Project Monarch Health suggest a 20% bleach solution. Look in the section on rearing Monarchs. Also, thoroughly wash the milkweed before using it.
I feed young caterpillars tender leaves and older caterpillars older leaves. Don't give older instars 3-5 young leaves. Don't give 1st to 2nd, older leaves.
Make sure leaves are dry. I also use a papertowel in the bottom of the container were I raise them. I clean them morning and night. If they haven't eaten the milkweed all up, I just take out the paper towel with the frass and put the milkweed back in. I put a 5 oz paper cup in the middle of the 13 cup glad container, drape the papertowel over and lean the milkweed. Don't forget to put the top on (tops have small holes that I put in with a corn holder). The raised part made by the cup helps the frass (poop) stay off the milkweed. I change the papertowel, but not the cup. I go through a lot of papertowels during butterfly season.
That is what another person who is having trouble on the Monarch Teacher Network is going. He is resterilizing every thing. It is a lot of work. I hope this helps. http://www.eirc.org/website/Programs-+a ... twork.html
In case anyone is interested, this is info on Monarch Teacher Network.