Hey Joe,
Dice like constant temperature and low humidity. Probably around 60 to 65 degrees(Basement) with low humidity and not a lot of natural light.
The dice you show have extensive "crystalization" and will eventually just break apart into a million little pieces. Probably from improper storage.
Over the years the material that dice are made of has changed. Some are Cellulose Nitrate, some are Cellulose Acetate and there are probably others.
Some dice actually shrink or "implode" over time. I have had some where the spots have fallen off the dice.
If you have dice that are starting to decay or break down it is best to not store them near good dice. One thing that you can do if you are unsure is to smell them. Sometimes dice that are going bad will have an odor of vinegar to them.
I have a pretty nice dice collection, but they always worry me. They are far more unstable than chips and I don't think they will last real far into the future, but they are fun and colorful and I enjoy them.
I am not an expert, but I hope that this helps a little.
Peace,
Don