I have to ask JJ, cuz I had an issue with another soft plastic, were the baits cold when you noticed this? I got a fluke type bait and put it on to fish and it was really hard...like you said, like tire rubber. One thing I did was to heat water to a bubble - just before boiling - and dip the plastic bait for like 2 seconds then check for suppleness. Let it dry straight.
I saved a whole bag in about 10 minutes.
Give it a try, it may on may not work, but it's worth a shot IMO.