I am sorry for your loss.
If the vet did not give you medication for ALL of your gliders to treat the parasite, please take your other gliders to the vet for examination and treatment for the parasite. It is 99% likely that they also have the same parasite.
You are not a bad glider Mom. Many gliders have come to new homes with parasites.
For other folks reading this thread: This is the PRIMARY reason we tell everyone to quarantine new gliders. She or one of the other gliders may have had the parasite before coming to your home. Unfortunately, gliders hide their illnesses and are often very, very sick before showing any signs. Sometimes one fecal testing will miss parasites that are in a dormant phase. That is why a repeat testing after 30 days is so important.