I think it's important to find out what happened to cause the change...it's a pretty drastic one to have occurred for no reason.
It's hard to hear this, but you can't care more about anyone's life than they do- especially once they are adults. I told my kids this all the time. It does no good and you can't force them to study and turn in assignments at this age.
As far as college goes- I only paid for my kids' classes if they earned an A. They were capable of getting straight As, so they could have had their college entirely paid for. It ensured they had skin in the game, and it saved me some money!