It sounds like you may have gotten some kind of chemical on the feet.
I'm melting!!
Just reached for the controls of my Jolida102 and came away with oozing black slime. The rubber vibration dampening feet seem all to have melted. Scraped them off. Replaced with baby-food container caps. I assume this will work? Shouldn't rubber designed for hot amps be able to resist heat? (or is this just what happens as they age ...)