I'm no expert, but I've heard that the ideal hen:rooster ratio is 10:1. If there are too many roosters, the "odd man out" might be harrassing the hens or somehow his mere "loser" presence might be detering the hens from laying.
I am of course suggesting that you eat one of the roosters and see what happens. JMO
On the other hand, too many hens can disturb the pecking order just as easily.