Yes.
A. Will the wider tire fit on the rims ok to hold the higher air pressure of a D compared with a C ?
B. will the wider tire rub against anything in the wheel well? On ours, there is a metal LP gas line going between the tire and frame on the driver's side of the trailer. Can't go fatter tire.
C. A taller tire might also not fit in the wheel well above it. 75 is the ratio so wider is also taller for the same 75.
D. Taller tires might rub together if the axles are close together.
E. Wheels have weight ratings at tire pressure too. Going from C to D might not be ok--depends what the existing wheel specs are.