yellowing of shower stall fiberglass floor

It's a fiberglass shower right?? Mix Whisk 2X HE laundry liquid soap with 20 Mule Team Borax ...into a paste (don't use water)...take a damp sponge and apply to the floor and walls. Let it sit for a few hours (overnight is okay, too). Then hose it down and see what it looks like. Might have to do this once a week to get it looking nice again. This is just part of my regular routine.
Works in the bathroom sink, too.

Watch that floor... it might be slippery !!