Tastes like sour milk-Not kefir, what did I do?

What did I do wrong? My kefir is rotton, tastes like milk gone bad. I have had kefir many times, this was not kefir. Can I salvage the grains? Is it all contaminated? Can I start over? Its not thick like kefer either, its milk with a few blobs. I guess I put it in the fridge too early or did not change the milk often enough when I got it.

~gracey Tweet