That looks like ich and potentially flukes or black ich as well, but it's hard to discern from the photos.
Ich should be treated with copper because your hippo cannot tolerate CP. black ich can potentially be helped with prazipro dosed 5-6 days apart. They can be used concurrently, although I would start copper first in quarantine and make sure you keep up on water changes to avoid ammonia burn. Get the ammonia alert badge by seachem to show you when a large water change is necessary.
The fish will need to be in fully therapeutic levels of copper (coppersafe is my preference - you'll want 2.0 PPM) for a full 30 days, testing daily.
Don't use amquel, prime, or any ammonia detoxifying products with these medications while in QT as they'll turn the meds toxic.