Sudden problem with turntable

Before trying anything that will cost money... Did you try putting the same lp on that you listened to last? If so, it could be you're now listening to an inferior pressing?

Could you or someone bumped your counter weight and added tracking force, your head shell screws were loose and cartridge moved, to troubleshoot you could back off on tracking force or adjust vta. Did you check the suspension of cartridge was riding low close to album? I use magic eraser, I have a vpi machine but get best results cleaning albums with a hand held steamer with cleaning solution and rinse with lab water or distilled . Hope you find problem it can be aggravating, been there.

I tried the magic eraser and that wasn’t it. I think I will need to check everything from scratch, including cartridge setup, platter level, ball bearing lubricant....Never done that before so it should be a good learning experience. The odd thing is it seemed to happen quickly went from sounding good to slightly slow or hollow. Just missing something and I can’t put my finger on it. Very annoying. 

Go to Vinyl Asylum and download the best protractor for your arm, put it on your table and follow the lines it's easy. If you think it's low on oil maybe from shipping don't use it till you top it off, look in there with a flashlight. First thing I would do find recommend tracking force for your cartridge and see what your tracking force is set at, to much force will dull sound. If you don't have a tracking force gauge make the arm float with the counter weight,set dial to zero without moving counterweight, then turn counterweight to cartridge recommended tracking force. Just be careful of not damaging needle while making it float. 

I'd vote against that last suggestion. You can get a surprisingly good digital stylus force gauge in 2 days or less on amazon for about $11. Cheers,
Spencer