I have 2 adult cats and 2 new kittens. when I tried giving them Kitten food they refused! All prefered the regular food. I tried a few brands (from the poor selection of good food we get here). Is it Ok for them to eat the regular food? I know it can't be too bad as I see my out-door cats who are healthy and strong even if they get the cheapest kind... But is there anything I can or should do?