after a battle with fleas, which i learned a couple of my kitties were under weight and one was diagnosed with Flea allergy Dermatitis i bought my Kitties a tube of Nutri-cal to supplement their dry food at first one of my kitties loved it as would have eaten the entire tube in one sitting but as i've slowly switched from Purinia cat chow to the better dry food of American Journey grain free salmon cat food he's stopped wanting to take the nutri-cal supplement is this normal or is their something wrong in the second half of the tube? none of the others has ever cared for it and its a battle to get them to take any i just feel its odd that he loved it fr about a week and a half- two weeks and now acts like the others is this normal? or should i throw out the rest of the tube because its somehow gone off?