[Question] Difference in gummy champ plastics

[Kilgorettrout]

I have a few gummy rhynos. My favorite is very gummy, even floppy. The others which were a newer run, are not really gummy at all. My favorite was made I believe in 2011 and the newer ones in 2014. All three are Sanny molds. The newer two were sold as Xg, and the old just had a ch gummy sticker on it.

I was wondering, is each run totally different, or were they floppier years back? Which runs are the floppy ones I like so much?

Thanks for any and all help.