trail shoes

Hi guys! I need some help with this. I currently have a pair of trail shoes (Brooks Adrenaline) and I wore them for a 50k trail run. I ended up with 5 black toenails. I know I have to make an adjustment before I do another ultra. I was at the Chicago Marathon expo and asked the Brooks rep. about this. He had me try on the next size up but, it seemed too big. I also have wide feet. What shoe should I get? Most of the running places around here do not know anything about trail shoes. Same thing with the Brooks rep I talked to. I usually wear a size 8w in brooks and have never had an issue with my feet. I thought I heard somewhere that for ultras I needed to go up a size. Educate me in trail shoes and how to solve this problem. By the way, I love this ultra stuff!!!!