Aquariums: Help! Blue parrot is poorly

Hi everyone, looking for some help with my Blue Parrot. He’s been like this now for 3+ months now and we are running out of ideas. We have treated for swim bladder as advised from the fish shop, done a parasite treatment and kept up with the usual water changes. We have a whole array of other species which are fine however it’s just this one that is like this. We have put him into the fry tank now to keep him out the way of getting nipped. He will lay there all day and have a slight burst of energy when we feed but usually picks off the floor. I’ve checked the water quality at home and taken samples to the shop and it’s fine. Any ideas please 🙏🏽