My TK armor has yellowed like many and I may have found a way to stop that although I have no way too test this out myself, other than to share my knowledge. I am very messy with CA glue. This is the start. i have noticed that where ever the thin CA glue dripped and ran on my suit, that spot or run underneath is still white. Everything else turned yellow. Perhaps dipping the armor in thin CA glue may prevent this.  I do lots of parades and outdoor trooping in heat. Here is a crappy photo of one