underfed means plant lacks essential nutrients, doesn't necessarily mean you have to feed every watering
if the soil is rich enough, that provides all the food it needs
however, i think that is unlikely in this case, a soil needs quite a bit of nutrition to feed through flower(by itself)
if it ends up in rich dirt outside, it might be just fine, but that may be tough to call
so if you have rich organic matter to toss in the transplant hole(or pot), that should feed a while, composted manure would be good