My cat Snukums is an eight year old short-haired tabby. About four or five months ago, I switched him to Nutro Indoor Senior catfood. He did well with it for quite some time. I even noticed that he had stopped coughing up hairballs. About three weeks ago, he started producing hairballs. Lots of 'em. He's thrown up three times this week and when he did this morning, it was just catfood. He is brushed regularly with a shedding blade and the amount of food is controlled. Could I be missing something here? What would cause a streak of no hairballs, then a sudden burst of them?