Fish moves less than others?

Hello friends, I have a few guppies in my aquarium and they are moving happily and cheerfully and swimming back and forth.

One, however, only comes to swim to the others every now and then and mostly hides.

Could it be that he is sick?

I also noticed that he is more active when the light is off. Is he perhaps sensitive to light?

Water values ​​seem to be correct so far.