They can self regulate hunni, he may just be going through a stage of it at the mo. They can also get fed up with their food and hold out for something else... cheeky buggers!
I think if Harvey bear is fine in himself and is drinking ok then I wouldn't worry just yet, as long as he isnt losing loads of weight too he will be just fine
Bonnie can be funny like this too and she eats the same, dry with wet, I tend to change the wet from time to time so she doesnt get bored with it