DMI is based on your players game shape and skills, so if your players GS or skills improve his DMI will go up too, and in your case the DMIs werent changed during off season processing so they got changed today based on your game shape, so your team didnt get worse or anything..... another thing DMI helps with is scouting other teams, if any of the players is in proficient GS and his DMI is lets 55000, and his salarys only 2000, you know that hes been training that player..... thats basically all i knw about it.