Tri-X has something like 16 stops of usable exposure range.
OP said foggy flat scene which probably means like 8 or less stops of range.
Properly exposing it will place it in the lower half of the film's total range....
He over exposed it so it shifted UP by two stops which really isn't a big deal.

Development time changes the contrast of the film. If he pulls it by 2 stops, it'll really be flat.... it was flat to begin with. He will have to compensate it when printing, if that's even possible.

Assuming my assumption about the scene is right, he isn't hurting anything by developing it normally.... it's still well within the film's capability. He'll have a bit longer exposure at the printing time but contrast will be pretty normal. He may have to boost it just a little, if that's necessary.