My robo hamster also like that.. Is like the skins are wet wet looking.. I wonder is it because of the pee or bedding that cause them like that.. But whenever i clean the cage, I use a wet cloth to wipe them cause they smell darm stinky.. After wiping and drying them, their fur become like normal.. Few days later, they will become back the same.. Wet wet looking..   

So i think is normal, no worries..

maybe can try gv them bathsand?
my robo dun hv such wet looking problem so far~