I would be tempted to put the slight drop-off in form down to the moral-lowering effect of Hughton's impending sacking, rather than the fact the players weren't playing for him anymore.
That might be tempting, but how does that fit in with the apparent shock from the players when he was disposed of?
TBH it doesn't really, although we never know how much faith to put in public statements.
Maybe Hughton knew he was about to be axed and his own day-to-day motivation slipped a bit. Couldn't blame him if that was the case.