I fly sailplanes and use lots of flap to slow for landing. Of the 8 planes I have used flaps,on all required a good bit of DOWN elevator to keep the nose from pitching up when the flaps are dropped.
When you drop flaps the trailing edge of the wing drops. If you draw a line from the leading edge to trailing edge of the airfoil flaps up and flaps down you see the incidence angle of the wing increases when flaps drop. The incidence angle of the horizontal tailplane is not changed so decalage increases when the flaps come down, so the plane pitches up. It is similar to rotating the wing such that the trailing edge moves down. To restore decalage to the value for balanced flight you need to change incidence of the tailplane by dropping the trailing edge of the elevator.