my tutle keeps its eyes closed

by angelica
(Bacolod City, Negros Occ. Philippines)

my baby red ear slider always keeps its eyes closed and likes to stay on its basking rock. when i put it in the water it opens its eyes and when its sunning its eyes are fine and its active. he eats and he still swims. is this just a vitamin A defficiency or something more serious? or does he just have a knack for sleeping now?