How to fix gap at top of french Pvc Doors?

i have a gap at the top center corner of the right door which the left door hooks into i can see daylight coming through the top and have a draft. i used to have the problem on both doors but adjusting the keepers on the door and top of frame fixed the left door but not enough on the right! when looking at the door you can see it slopes down and the hinges on the outside are sitting clearly 1cm higher in their socket then the other side and the door slopes can i fix this by adjusting the top hinge as this looks like it is pulling the door down??