How to restore yellowed linoleum on pup floor?

Over the last 3 days my nice white floor turned yellow. I have the pup outside and open for our repairs, the roof is detached so the sun was shining on the floor during the day. The kids cleaned the pup with Windex and now the floor that was white all these years is yellow! Any ideas how to get it white again?

 

I’ll buy some stripper and do a test. Thanks for the advice.