I have an old kitty that was suffering from fleas this summer. I gave him the Hartz product about 3 weeks ago. He has gotten sicker and sicker, and now isn’t eating much and has no energy. I’ve been chalking it up to old age, but I just saw the news special last night on the Hartz problem and I’m worried that I might have made him sicker. He’s not having convulsions but he is listless and won’t eat other than a few bites at a time. Any suggestions?