WHen my leaves on my hedychiums turn yellow, they also tend to turn crispy, and its because of not enough water. Most of my stands of hedychiums are well within sprinkler water range, as we have been very short of rainfall this season so far and it looks like we are going to stay short. A few stands have to be hand watered, and if I forget, they start to yellow, and if I REALLY forget 2-3 days in a row, they get dry burned areas on the leaves