AMD has released a brand new driver for its graphics cards. According to the release notes, the AMD Radeon Software Adrenalin 2019 Edition 19.1.1 driver improves performance in Fortnite by up to 4% on the Radeon RX 580 and by up to 3% on the Radeon RX Vega 64 graphics cards.
Source: N4G PC AMD Radeon Software Adrenalin 2019 Edition 19.1.1 released, improves performance in Fortnite