Weed and feed already has fertiliser in it - that's the 'feed' part, so you don't need any extra. But I would say you shouldn't be using weed and feed now, it's too late in the season. That should be applied around April and again six weeks later, then no more. There are autumn preparations for the lawn, but these don't contain weed treatments - the weeds won't be growing strongly enough to respond to such formulations at this time of year.