Carl

Don't pitch in the connection note. Don't pitch in the first message after they accept. Ask one question you would only ask someone with that job.

It is hungry, not dead. That acetone smell and the grey liquid, which is just alcohol and water, both mean the culture has eaten everything available and moved on to producing byproducts you do not want. Feed it more often or at a bigger ratio: go from 1:1:1 once a day to 1:5:5 once or twice a day, and the smell will move back toward yoghurt and green apple within three or four feeds. Doubling in six hours at two weeks is a genuinely good starter, you are just underfeeding it.

Also worth checking your oven with a separate thermometer. Mine ran 20C cool for two years and I blamed my starter for all of it.

Save the validation response, not just the outcome. A dated record of the check has settled this for me before.

And if it does run warm, cut the starter to 10 percent for retarded loaves. Solves it without buying anything.

"You need 12" reframed the whole thing. I had been comparing 900 to 40,000 rather than 12 to 270.