Hello,
I'm very, very sorry to hear you lost them
I think if sand got in their mouths they would likely push it out.

The temp was WAY too high!
This especially true for the auratus ! !
78 degrees F should send up the red flag !!!
They will do just fine with 70 - 76.

I hope that you try again
Don't let the temp get above 78F.
A sustained temp above 80 is very dangerous.