Yes actually it is. I’ve had him for 3 years going on 4, he’s my oldest fish. He only sticks to one corner either on the top of his vine, or the bottom of tall plants. Occasionally does a swim to the other side of the tank if im looking inside. He’s one of the only fish that don’t come to the side where I drop food in when I do.

Your caution is good but I assure you he’s alright (I think). If he is ill he’ll start to show some sort of physical symptoms like sunken in stomach or extremely pale colours. And especially if you have other fish if he is weakened they’ll kill him quickly. When my peacock had internal parasites the other fish took him out in minutes once he began to decline.