Did the disc sit in the sun light ever like near a window in the basement, some plastics can get gummy in that respect and loose some High Speed Stability on the way.
Nope, it was just sitting in the middle area (not near heat, not near sun) sitting 2nd from the top of a stack of 4-5 discs; nothing special about the stack. The disc on top of it was a 168g Sol from last year's ace race... despite the smaller diameter of the disc, I can't imagine 1.6N force in perpetual 60-70 degree F temperatures to compress the dome enough to make a noticeable difference?