Nothing to do with age I have a team at 21.6 av years & so far only one booking (yellow) this season & I change between Hard & Normal most games .I´ve never heard of "Soft" but if you mean the option easy I´ve never tried that .
Also I don´t think there is any proof in the win bonus for matches having any affect on the game.
The only thing for your situation would be if your players were at low moral or condition but they look fine ….so maybe it´s just bad luck ?