So I brewed my first milkstout 14days ago. Mashed at 68C Used 450g of lactose with OG at 1,060. Used Mangrove Jack M15. Fermented at 18C. My problem is the gravity is stuck on 1,028. My next step/plan was to add cold infused coffee. Do I just add the coffee or must i heat up and see if I can get the gravity down?