I have a Toro LX420 riding mower. I had to replace the blades, and the parts department did not have Toro brand blades, said that universal blades would work. Since I installed the blades I have had to raise the mowing height two notches higher than I normally mow to keep it from scalping the grass, and it seems to be harder to steer.Could it be the blades or something else that could be causing this problem ?