Help on baking in the stone based oven sourdough

Dear all until now I have been baking with success in the Dutch oven sourdough bread with good holes and crust. the starter  is very good and never had problem since I move to stone based oven. I am using 250C top @240C bottom and steaming once at the beginning .

I have a big stone based  steamed commercial oven  and can bake 6 loafs at the time . but the result are really bad

I m using % 75 hydration

bread is coming out flat and very sticky, is there a way I can improve.? could you recommend a way or a book for commercial ovens

do I need to prove it long time ? is there a structure of basic steps I need to fallow , I am open to change the way I bake, 

I am using  200grm of starter for each 1 kg flour and 700 grams of water and add the 50 arms water with 25grm salt.

I do 4 fold every 30 mins for 4-5 times and I weigh 1 kg,  and places the dough in a basket raped in cotton sheet and leave  overnight in the fridge . I take out the dough from the fridge and  to start baking in the oven   

I use %13 protein organic flour and my starter is organic too.

any help or tips appreciated