Graphite is the trickiest color for me too, black is usually the thinnest in any brand of coatings and a little finnickier than the rest in my experience. Humidity definitely screws with it more than the rest. Bigngreens advice about covers it.
You need Armor Black Cerakote if you want the flat.The main problem is the graphite black. Im pretty sure its humidity, very hard to get a matte finish out of it. If the humidity is high i get a gloss black out of it. I call it black ice, almost looks like a "wet" black. My only complaint on wear is on the bolt or a barrel in a pistol slide, just doesn't hold up well.