Dead Shrimps...

I think one of my tank is having issue...

So far, within one week, I had about 5 shrimps death...

I do see shrimps eating well, active, pooping, few femals carry eggs, plants growing well and I see some baby shrimps... what is wrong with shrimps death?

I also even checked my water. Nitrite, nitrate, ammonia is all 0 and pH is 7.2.

I know pH should be 7.0 or lower but, I don't think 7.2 will kill shrimps because I have few shrimps that had 7.2-7.6 pH and they breed like crazy.

I don't have GH and KH test kit... so, I can't test them...

I don't want to reset this tank because it's only been setup for 3 months and I don't think there is anything wrong with this tank.

I do water change 10-15% every 2-3 weeks.

I hope I don't have any more shrimp death...