Carl

You can also bulk in the fridge for part of it. Two hours on the counter, then into the fridge for the rest, then shape cold. Not traditional but summer is summer and it makes the timing controllable again.

Update: bulk cut to three hours 20 minutes, ended at about 60 percent rise, same everything else. Loaf came out 9cm tall with an open crumb. It was the clock.

I have been going by the four folds and the clock rather than the volume. So a slack, soupy dough at hour five is the symptom rather than a hydration problem.

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.

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