it may be normal, what kit? are you sure it's a warp and not washout? does the warp go from root to wing tip? slight amounts of warp/twist in a wing may be designed in. if it is warped the covering trick works.....it will tend to move back over time. best thing to do is remove the warp now building the wing stright before covering, you'll probably have to remove the sheeting and start over.

John