...another take.....if your t/t is belt driven and getting on, the belt may have stretched.
Turntable weight affects speed
I tried a Thorens tt weight on my Thorens TD-850 belt-drive tt. It noticeably slowed it down. It seems like extra weight on the bearing would affect any tt, but what do I know? Is a speed control (and strobe/test pattern) generally required to use a turntable weight while maintaining the proper speed?