Yeah, it does sound like HLLE. If the scratch stressed it out enough the stress could have brought on the HLLE. Do you have a QT that you can put it in to observe it alone for a while? Also, try to soak the food in vitamin drops for a while before feeding and be sure it's getting a fair bit of algae sheets to nibble on. You can also chop some garlic up to soak the food the food with, which will help it's immune system.