I usually use hasta grow to feed all my plants. Love what happens when I use it. BUT ... no way anything in my yard needs more water! But they are looking like with ALL the water they have gotten that they are missing something. Especially the flowers... I have loads of leaves on everything but not much has flowered like it usually does. I know some of the reason is heat (we haven't had what we usually do by now) but I have also usually fed stuff a couple of times by now and with all the water I have't fed at all this season.
In sandy soil, nutrients can certainly get washed away quickly. A quick foliar feed like fish emulsion (diluted!) can help. I think the alfalfa pellets are a good idea too; but you also want something for potash (like wood ash) and phosphorus (side dressing w/ rock phosphate, maybe). In my heavy clay, nutrients stay around forever.
But I agree w/ Len123 that giving the plant time to recover first is the best course.