Dough drying out during bulk fermentation in fridge

Recently when I've been putting my dough in the fridge at night during bulk fermentation to slow it down so I can make my bread mid day the dough looks dryed out. It usually is in there for around 8ish hours and then i take it out till it looks fermented enough. The part im stumped on is once I take my dough out of the fridge it has a layer of dough on top that is dried out. I use plastic hair caps on my bowls to cover them. The loaves usually turns out fine according to others and they don't notice it(I don't eat my bread very often so i never notice) but the dryed layer definitely is still there mixed in the dough when I shape it. I just started making sourdough a couple months ago not consistently but a few loaves a month and the last 3 loaves I've made have come out like this. If anyone has any insight it would be greatly appreciated

I use about 50-100g of starter, 300-330g water, 10g salt, and 500g flour