I asked a friend who breeds fish and works on aquariums about this today morning and he said it could happen for a lot of reasons the most common one being stress. If the water levels are okay and there isn't anything in the tank raising the ammonia level, coupled with the other parrot getting better, then its just stress and it will get better with time. The biggest help you can be to the fish is to give them hiding spots (which you have) to reduce stress and test the water things will be just fine. You can also keep the water fresh with a 35% displacement but you also said your friend is coming over to give you the low-down on the tank so I'd wait to hear from him first before doing anything else chances are they are just getting used to the new surroundings and the stress elevated in the process.