I had one girl slug out this season as well and another lay 4 slugs and 2 "boob eggs" Those two are at day 34 and look pitiful but there is a living snake in each LOL. Yesterday I had a female lay 5 perfect eggs and 1 slug.
I use belly heat on my animals but I talked to one breeder in my area that says since he switched to back heat he has cut down on his slugs considerably. Maybe a coincedance? Not sure. I think my next rack may be back heat tho.
were your females too young maybe? or under/over weight?