I'm following an apple sculpting tutorial and at some point, I seem to have accidentally deleted a vertex along with the four adjacent faces. I filled this hole using the methods I've learned thus far (used F to fill between vertices and Ctrl+R to add one vertex in the middle)
The apple now looks fine in edit mode, but when I switch to object mode, the faces appear to be triangulated. Furthermore, when I apply a subdivision modifier as instructed in the lesson, an unsightly patch appears where I filled the hole. Merging vertices by distance had no effect. The normals are not reversed. I'm using version 2.91 if that information's relevant.