My bet would be on the tank not being finished cycling yet. Corys can be pretty sensitive to water quality & especially don't deal with
ammonia in the water. If the tank has cycled fully then it is possible the cory just needs time to settle in. Are there more Pandas in the tank to make it feel comfortable? My money is on not cycled properly though. Do you have ammonia,
nitrite &
nitrate test kits? If you do, what are the test results. If you don't, I strongly urge you to get an
API master
test kit. If you buy tests other than the API ones, make sure they are liquid tests as the paper strip type tests are usually quite inaccurate.