I notice there's a fair bit of bread-making expertise on the forum. I want to know if I've knackered my rye sourdough starter. I've been away a few weekends and neglected to refresh it. It seems to be still alive, but has separated so there's an unattractive greyish liquid, and smells more sour than usual though not horrible. Is this of sinister import? This particular starter dates back fifty years so I am loth to let it go...