Reptile & Amphibian Forums

Hi.
I bought two female hissers on the 2nd of April this year. Later I decided that I wanted them to reproduce so I bought a male on the 1st of June. Now, in the beginning of July, I was surprised with 25 baby roaches. I had read all over the web that it takes 60-70 days for the nymphs to develop, so I'm puzzled about how can these be born at this time. I believe that either:
1)one of the females came pregnant from the store, but kept the nymphs inside her for 3 months, far exceeding their normal time to come out.
2)the male mated with one of them immediately after coming from the store in June, and the newborns came out really early, after just one month of gestation.
Is it normal for the gestation period to vary this much? I cannot understand.

From which instar am I going to be able to check whether the roaches are male or female?