Brand of basic fertilizer makes no difference usually. Keep the nitrogen low and if over 10-10-10 sprinkle lightly before a rain; if all 10's or less can put a little more on. Rebloomers take more later in season so good to keep them in separate bed so the others don't get overfed. I have watched 2 front lawn iris beds each on a steep slope for almost 10 years; none has had fertilizer or weeding but full mowing around a month or so before the killing frost. They come back, they bloom. Of course not as nice as other gardens but they are survivors.
