Response A
2.1s164 tok$0.0031
It isn't ruined. That acetone smell means the yeast and bacteria have run out of food and are producing more acetic acid and ethyl acetate.
Feed it more often: discard all but 50 g, then feed 1:1:1 by weight twice a day for two or three days. Keep it somewhere around 24 °C. The sharp smell should fade into a mild, yogurt-like sourness.