Sourdough Ciabatta

Hi All

I tried a sourdough ciabatta for the first time last night and have a few questions to put to the well initiated bakers out there. 

Recipe:

1000g stone ground white bread flour

300g sourdough starter 100% hydration 

850g water

20g salt

The starter had bubbled out of its tub and floated well, so I thought it was perfect to use. I mixed it with 750g of water and then added all the flour. 

I let that sit for 30mins. Then I added the salt and 50g more water and gave the first turn and fold. 

20min wait and then 50g more water and turn and fold. 

At this point in the instant yeast version I would see bubbles and the dough would be feeling a bit light and the gluten would feel like it had developed. This was not the case now. 

20 mins next turn and fold and I decided to take the dough out onto the table and work it, maybe it needed a more vigorous work out. Well, I work it for about 20 mins and it still felt like a wet sticky mess. So I put it back into the bowl, wrapped it up and put it in your fridge for 6 hours. 

When i took It out the next day, there was very little fermentation. I let it get to room temp. Put it on the table, folded it and divided it. Let it sit on the couche for about 2 hours and baked it. (4 loaves) 

The oven spring was average, texture was good, airy with enough holes. The colour was fantastic. But why did it not want to develop the gluten when mixing ? 

Was the starter not strong enough ?

Do I need more starter in the recipe ? 

Puzzled indeed...

thanks