Neon tetra behaving strangely?

Two days ago I put six neon tetras in my tank to start (its a 30 gallon with a 90 gallon 403 fluval filter) and they all got along and all of them are obviously comfortable in their enviornment but one of them is behaving strangely. he swims around find but its obvious hes broken from the school and hasnt been with them all day and now hes just being static in one spot, help?