Monster Zero x SciFi Japan - Archive Only

I picked up the below Yamakatsu figures off of Ebay for a pretty decent price of $10.00 - I am not sure of their value but I think it is a good deal for a 1984 figure set



My question is that when I got them I noticed that where the figures were touching the plastic bags the rubber had seemed to yellow. I removed the figures from the bags and on most of the raised ridges they were in fact yellowing. Is there any way I can remove the yellow from them or is it best just to leave them as be? Thanx!

I'm not entirely sure since I'm not familiar with the figures, but trying warm (not hot) water and a mild soap are definitely a good and mostly safe place to start. Water alone might even do it.