HELP!! What Is Wrong With My Platy?

What is wrong with my platy?

It looks very much like whitespot, aka ich. You can see the fish more clearly than us - does it look as though it has been sprinkled with salt?

If the fish does look that, it needs to be treated. Because of the life cycle of the whitespot parasite, the whole tank needs to be treated.
You have 2 options.
1. Raise the temperature slowly to around 30 deg C and add salt - though this does depend on what else is in the tank as some fish are salt intolerant.
2. Raise the temp to 30 deg C and add a whitespot medication. If you have shrimps and/or snails (that you want to keep) you will need to remove them from the tank.

For both methods, do a thorough substrate clean before starting treatment.
If you choose option 1, you need to add salt at the rate of 2g per litre for 10 days. Use aquarium salt rather than table salt.
For option 2 there are several brands on the market, use whichever one you can get tomorrow. Remove any carbon in the filter before adding the medication. Add to the tank exactly as the instruction tell you. The parasite has a three stage life cycle. Stage 1 is the spots on the fish. The parasite is protected by a coating and the medication can't get at it. In stage 2, the parasite falls off the fish and multiplies, still within the coating. Stage 3 is where the coating opens and the new baby parasites go looking for a fish. This last stage is the only one where it can be killed; there must be some medication in the water when the very last one gets to stage 3. Stopping treatment too early could well lead to another infection.


After the whitespot has been totally removed, water changes will get rid of the salt; water changes plus new carbon in the filter will get rid of medication.

Don't forget to turn the heater back down 

That is definitely whitespot, so treat the tank with one of the two methods I gave you.