URGENT! OVERCLOCK FAILED WITHOUT OVERCLOCKING

Pc specs: Asus X99-A, 16gb ram g skill 3000mhz, 2 gtx 980 ftw sli , 1000w corsair hx psu .

My pc is having an error while playing some games like dota 2 or fortnite going black screen (no signal input) and the pc keeps on running the only thing that shuts down is the monitor and the main gpu fans . In other games like call of duty modern warfare , gta 5 , csgo , rainbow six siege everything works fine with no problems . I need your help !