At 7.8pH, ammonia is much more toxic than it is at lower pH levels. Thats around the point where ammonia starts to become a problem even at low concentrations. So you need to make absolutely sure your ammonia is low to zero.
Your pH is quite high, possibly much higher than the store water. So pH shock becomes more of a factor. Maybe a lengthier drip acclimatisation will help. On the plus side, a high pH makes cycling much easier.
In case you arent aware, your test kit measures total ammonia which is free ammonia + ammonium. Free ammonia is extremely toxic, ammonium much, much less so. As your pH rises the proportion of free ammonia to ammonium increases towards more ammonia and so what you measure with your test kit becomes more toxic.
Are mollys more hardy than glofish. Definitely.