Glofish Danio Issue

[NYCAF95]

Have 3 Glofish Danios and usually they're playing chase all day!! I have noticed today that 1 of them is hanging out at the bottom of the tank... Just hanging in one spot at the bottom not really being active. The water parameters are good all the other fish are just being them, but this one isn't acting right.........

Very strange behavior and I'm worried about the little guy........ Any ideas???