Well bad luck, but maybe something else.

Keep upgrading those facilities! eventually it does help. It lowers the odds of injury when you upgrade your turf, and of course you get more red packs when you upgrade medical.

But since they are all MCs' maybe there is something in your formation or tactics that is affecting them more. One thing I do on my team is assign a lot of skillpoints to the Physical column of my MC's and DMCs, as they are the hardest working of the players.