sick platie?

If this is a newly set up tank, it is probably still cycling... You should read the stickys so that you understand the process. In the meantime you need to get test kits ASAP, at the very least for amonia, nitrite and nitrate. If you have to have the LFS test for you, ask for exact numbers. Don't just let them tell you it is "ok" or "in range" that really doesn't mean anything, especially when trying to figure out where your tank is in the cycle.

For now, until you can get test results, do large water changes, at least 25% daily. If you have high levels of amonia or nitrite that will help bring them down and make life easier on the fish (both are very toxic to them)
 
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