baby shrimp disappearing!

[trev1]

I have a 15 gallon tank dedicated for my 12 grade b crs and 6 fire red cherry shrimp.
they are both of breeding size and are breeding and i due count babies but at one point there were 30 or so then they started vanishing. i dont know why but i did add some gold apple snails and did not think they would be an issue. are they?
regarding water quality i tested just yesturday showed ph of 6.8 wich is low when out of the tap it is 7.8
and the hardness was showing soft. so i think that the snails and shrimp together are sucking the minerals out of the water due to shell creation and the young who shed so often due to there fast growth are dying cause the water is to soft.
am i nuts or is this possibly right...

thanks for your time

trev