Plastic bath tub stain from cleaning chemicals. PLEASE HELP MAJOR MISTAKE!?

We live in a mobile home and we are renting. We have one issue before we move. I was cleaning the bathtub with the works and it seems to have discolored the tub in different areas. I need to know what to do to fix this problem. It looks like dark rust marks on the cream tub but I believe it is marks damaged from the cleaner. I heard sand paper may work. How would I fix this problem to make the tub look nicer?Plastic bath tub stain from cleaning chemicals. PLEASE HELP MAJOR MISTAKE!?
After seeing your question, I don't have the answers to your questions, sorry :-(

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