Central Massachusetts zone 5b-6a; I had a small area of approximately 100 sq ft in my lawn that had low spots.

I needed to regrade and I re-seeded with a KBG and Fescue blend of grass seed late last fall. None of the seed I used had time to germinate. I have recently dominant seeded the area.

Would it be best to use a turf builder product with the weed preventer tencacity for crabgrass in the re-seeded area when I fertilize the entire lawn? Or could I use a starter fertilizer with a weed preventer across the entire lawn? (I would never use all of the starter fertilizer if I don't spread it out across the entire lawn.)

Will starter fertilizer on the established lawn cause a problem?

Thanks in advance