I've read where many types of leathers do this. Sort of shrivel up, look like crap and sluff off a mucus layer.
My cabbage leather does this now and then, matter of fact, it's going through this stage again as we speak. I don't know what is a normal, but mine does this every few weeks or so.
It really does look like crap for a couple days, but usually 2-3 days later - it's up again and looks better than before.
I've directed a powerhead near it to help it shed the stuff - but normally I just let it happen on it's own.