If you're a fan of the 2010-present The Outer Space Men action figures (with Glyos), it might be time to give them a good look. Mine have mostly been content to sit on a shelf for a few years, and I'd pull out some of the painted or glowing ones to shoot photos - but it turns out, they were quietly molting when I wasn't looking. If you look at packaged Mystron Infinity Edition figures on eBay, if the photography is recent, you'll notice some telltale glistening on some parts.
If you have 2010 or 2011 clear figures, or the painted Mystron, give them a look. Mystron's black painted wings, gargoyle gun, and tail have gone sticky for a lot of fans - you can wash them with warm water, soap, and maybe a very soft toothbrush or cloth. Meanwhile, it seems all of the clear (non-glow) figures from 2010 and 2011 are a little sticky - so your Alpha Phase, Beta Phase, and Galactic Holiday figures of Inferno, Metamorpho, Xodiac, Astro-Nautilus, Mystron, Alpha-7, Electron+, and Commander Comet could use a bit of a hosing down.
Further, any Galactic Holiday figures with vac-metal parts that aren't silver or gold may be discoloring the PVC of the figures. If there are Glyos pegs or closed fists around a vac-metal red/blue/green/etc. part, check around the hands or sockets. Alpha-7 and Gemini seem to be fine since there was no tight grip there, but I've definitely noticed some discoloration around the fists of Galactic Holiday Mystron, Cyclops, and others as I start to see who needs to be scrubbed a bit.
The same is true for a lot of Glyos figures from 2010-2011 - check your Pheydens, Sarvoses, Callgrims, and so forth just in case. Plastics sometimes molt a bit, or off-gas, or shed some sort of oils with time. It's good to check them regularly to see what, if anything, needs to be wiped down. I've got an old Kenner Bossk figure that seems to have extruded some of the yellow dye from his suit recently!