Weird Betta tussyae observations

Recently a Malaysian friend of mine send me some livida from Tg Malim and caught me some wild tussyae "Chukai, Terengganu" himself. Both are doing great and breeding and all.

But now we both have a problem with the tussyae: they give an x number of eggs and all/most hatch. Then when the egg sac is gone the number of fry starts dimishing. When the fry leave the nest the number is even smaller and keeps diminishing. He had 2 fry left from one spawn while I had only 1 left(!). Got a new nest again now though. At both of us the water is perfect, the food too. We just can't find out why this is happeneing to both of us.

So I was hoping some others could tell their experiences and let me know if they're perhaps similar or different, and perhaps suggest what the cause might be. I was thinking it is more specific species related in combination with the fact they're wild....but I'm not sure.