Let me ask you this.....Do you have a QT? HLLE is 100% treatable....if you have a qt with excellent water, a stress free environment, and good food , and vitamins...if it is the beginning of HLLE you can cure it....Just know it is not an overnight fix....
You should QT it anyway...a lot of tangs, especially hippos tend to carry ich...and since you really have no clue about the tank it is coming from...it would be in your best interest to qt....