Dead snowflake eel

Hello, I was wondering why my snowflake eel died, it was around 5 years old and around 20 inches, The water i had it in was good and it was just fine, two nights before it was eating and watching out of its cave as it always does, Then this morning i just found it outside its cave, dead. Its stomache turned green aswell, Could this have been from one of the silverfish i fed it? Or did it just grow old? Anyways, I put it in a jar of alcohol for memories sake. And its head has enlarged alot. nearly covering all of its head and can't see its eyes anymore. Is this caused by the alcohol or from the green bacteria in its stomache that it had the day it died? Also, this has happened a few years back. We put it in a jar of sweet water thinking it was dead, instead it popped back up in a few days alive! So, could this have been the same thing?