Also, last I checked, plants only change visually when you leave the area and then return. This may have changed, but if you really think they should have progressed but haven’t, try traveling a healthy distance and then coming back.
EDIT: Oops, didn’t really answer your questions. Fertilizer is not necessary. A hoe is not necessary, and you really only need a digging tool for when you initially till the soil. As Rose suggested, most likely you just haven’t allowed enough time to pass.