The best thing you could do at this point is get a fresh quail that has just passed and put him in a plastic bag and stick him in the frig, not the freezer, until you can take him to a vet for a necropsy to see just what these birds are dying from.
Aside from this, you need to go over your quail area with a "fine tooth comb" and look for anything that may be effecting them enough to kill them....Are they cold...are the quail dry...is it drafty where they are...is the feed fresh and bug free...is the water being changed daily...has their environment been disinfected recently, including waterers and feeders...do they have enough light...enough oxygen...exercise...mites...bugs of some sort.
As for symptoms...are they fluffed up...lethargic in the corner...respiratory ailments like sneezing, runny noses, lung rattles...how are their wieghts...what consitancy is the poop...what color is the poop...are they eating and drinking...
Anything that might send up clues. If they have been wormed properly and still they are dying, you may be dealing with a bacterial infection within the flock. You might want to try some Duramycin or Oxytetracycline in the water for a week or so and see if this does not stop the deaths.