Runny Dough

Hallo Fellow Sourdough Bakers,

I am a newcomer to the sourdough community - have made a few loaves now all of which have turned out far better than I expected. I'm noticing that the dough on the final (overnight) proofing is runny and fails to retain its shape, keeps the air in, just comes out flatter than I'd like. I'm baking on a pizza stone, have had better results baking in a Dutch Oven. All tips, tricks suggestins welcome. Many Thanks, Jagdish