I’ve had this starter going for about a month or so, which I refresh regularly with a combination of rye and wholemeal flour. It has always been quite vigorous and resilient.
I refreshed it two days ago, and when I opened it up today it had this peculiar, repulsive stuff all over the top (pictured below). It’s no longer aerated, and smells bilious.
Can I still use it? If not, how can I prevent this happening in the future?