Quail can be kept on the ground safe enough, however it is always recommended to keep their area dry. Use a roof, tarp up the sides, etc...during rainy periods. Like any other poultry area, too much water brings out all the bacteria, parasites and protazoa.
Have you wormed them recently? If they appear to be gasping for air without any respiratory distress (runny nose, watery or gummy eyes, rattles when breathing etc...), they may have gape worm. Not all that common in chickens, but quail are susceptible.
Other internal parasites explode with too much water...round worms, tape worms and even the protazoa Coccidiosis.
You might run a course of Safeguard through them. Either the Liquid or the Paste. This will kill off all the internal worms.
If you are seeing any symptoms of Cocci, (white diarrhea, bloody poop or diarrhea, going off food and water) you might use some Corid on them.
When your grounds stay wet too long, all kinds of pathogens and parasites breed to epic proportions. Birds develop immunity to their environment however wet too fast does not allow time for good immune response. It would be best to keep your quail areas as dry as possible to help prevent things that can harm your birds from taking hold.
