Who's product was it? If it came from Do-It give them a call.
I skip uv enhancer when doing glow. The plastic has to get to 350 degrees to be completely cooked when starting with raw plastic so I add the glow powder AFTER it has reached that temp. Left-over plastic can be heated to about 340 to get it fluid and does not need to go any higher. You mention the clear plastic start being a golden color sort of tells me you got it way too hot. How did you check the plastic's temperature? If you were not using a digital probe-type of thermometer like what Do-It sells you most likely trashed it with plastic that got too hot.
Plastic that has set for a few months can separate too and if it doesn't get a thorough shaking before using it again it can turn brownish because everything didn't get mixed well enough.
Glow pigment does not lose its glow capacity while stored IF its stored in a cool, very dark, very dry area. I have glow pigments that are 15 years old and glow like there's no tomorrow when given just a small shot of sunlight. Sunlight is, by the way, the best ever light source to charge glow baits and glow plastics.
