No, it has too low a nitrogen ratio to potash, you need a balanced feed, when they need feeding, which, if yours are in the ground, they don't, currently, its too late in the year really. If you didn't enrich the soil before planting with something like composted manure or good garden compost, then a small handful of Growmore lightly turned into the soil round the base of the plants shouldn't cause too much harm. A general topdressing, lightly turned in, with something like Growmore granules in spring is all they need, unless you didn't improve the soil, in which case, adding a mulch of composted material in spring is a good idea.