There is some crystallization on the orange/amber pair. I've been told this breakdown can infect other nearby dice so you might want to remove them from this group.
Cellolose Nitrate is the old & Cellolose Acetate is the new. I for one hope you're correct that Acetate won't but from what I've heard from people in the industry is that they both can.
As nitrate hasn't been used for about 50 years do you know how old that amber pair is? I would love to know my collection is safe as mine are all post 1970