You have too many roosters in too small a space. If you plan to keep multiple coturnix roosters in the same cage there needs to be 5-7 hens per rooster and about 3-4 sq ft per bird. With the number of roosters you have in that space you will continue to have problems. Fertility lasts for 5-7 days after breeding, so one rooster can easily keep 7 hens fertile. You stand to gain nothing by having more roosters in the same space. Often will fertility will actually drop because they are spending half their time doing territorial displays or fighting.