Thanks to you all..sadly she popped her clogs

I did check for any signs of her being egg bound and for signs of a cold - (two hens I also got at the same time from the same supplier had nasty nasty colds by the next morning, with one full of lice around her head...Careful nursing inc antibiotics and the hens now doing okay, hence my reluctance to return to this supplier)
Now you mention age I'm wondering if that would account for one of the quail having a broken beak, two of them having white patches where feathers have regrown as can happen in wild birds? None are laying, by sellers count they are 20 weeks old. Obviously I can't ever be sure of their age, could be they have had a hard paper round? Not yet old enough to lay? the boys have been crowing and mating since I got them back in Feb.
Ive been feeding them on a mix of chick crumb and fine chopped bird seed..Budgie seed and song bird mixed.. plenty of water and cover so they have hiding spots. Offered greens but they were not that fussed about them.
I'd like to up the ratio of boys to girls so need to find a supplier now that I can have confidence in.
And they always say sheep are born to die! sheep have nothing on these little guys!