Is my rooster ok

I’m imagining I’m overthinking things but is my rooster ok I’ve been feeding them the purina chick starter and some purina game bird crumble he’s about 6 weeks old and it’s about time to switch him but I have younger chicks mixed in he’s social and the center of our flock and is lethargic or sickly in anyway I just recently changed the brand of game bird feed to purina