Please help - leaven has changed - need advice
I was wondering what people think of this. I've been using this leaven for about a month now. It was looking fine and then one night I left it out without adding flour and water and the next day it developed an odd looking crust on top. It almost looks like mold but I'm just not sure - i'm relatively new to this. It smells very strong now too, like a chemical, almost like paint thinner. I'm thinking it's gone bad. Is this common? I had it in the fridge for about a week and then reactivated it and it seemed fine but then just all o a sudden turned on me. It's whole wheat and rye flour BTW. Any tips on keeping a leaven going?
Thanks. Here's a picture.