Hi Ken,
Cheers mate, I have a feeling that the male that is responsible for the low number of fry is feeling a bit threatened by the other males in the tank. I have a few juveniles in the tank that are now starting to sex out and they appear to all be males.

I'm looking at removing the young males from the tank so as to give him some peace and with any luck he will be able to successfully raise more young than he has. The Alpha male in my other breeding group seems to be more of an accomplished dad and has fathered seven fry at his second attempt, his first spawn was not fertile. I will be breaking up the groups again soon and will be looking to swap some males around.
Sorry to hear that you also have a male that produces a low number of fry. Hopefully when he starts up again after he is done finding himself he will be more successful than he has been so far.
There has been a real clamour for females recently, personally I think that having a sufficient number of males is just as important. From experience to date not all males are good fathers so if you have a number of them you can swap them around until you find one that displays good parental skills.
Thanks for the advice.
Adam