Just a thought:
Could it be possible that whatever you are feeding your fish changed the color of a regular bubble nest? Because whenever a piece of flake food gets stuck to the glass on my fish tank, it starts to deteriorate and the color dissolves like a dye. Are you feeding red flakes of any kind?
It couldn't be anything about the food.. the only colored food I use is the usual processed flake and granuals.. that stuff is gone in minutes. This thing is about the size of a racquet ball... it would take a heck of a lot of food to color it.
The idea of a dead fish is possible.. with a miasma of goo around it. I'll wait until monday to give it a chance to hatch if they are eggs and then I'll net it out for further scrutiny.