I did a very informal wedding this weekend in the worst possible lighting situation- yellow lights in a metal barn. I used several different lenses and my sigma flash. All the pictures are on the dark side even when my flash was turned up to full power. When I was doing the family pictures I took several of each group. The first was OK and the second was underexposed and had a very yellow tint even though I changed the batteries frequently. What did I do wrong? I seem to also be having trouble with my flash having a slow recycling time.

