Late Blight?

Crap. I may have found late blight on my Brandywine tomato plant today. The weather has been pretty wet and cloudy this season and although I started my plants from seed there are a lot of other gardens in the neighborhood and I'm pretty sure most people buy their plants-some from the big box stores. Last week I retied all the plants to try to get more air circulation between the plants and I try to check my tomatoes everyday. noticed this leaf today. I pulled it off (along with the other branches on the bottom part of that plant) and am scouring the net for pictures.

The reason I'm not sure is that I found a slug on the same plant yesterday and I sprayed it with ammonia, I'm sure I got some on the leaves and I'm wondering if it's a burn mark. I only have really tiny green fruit on the plant now and they look fine.

I just read this description of late blight: "The disease creates coin-sized black or dark green lesions on the leaves and fruit of plants, surrounded by halos of white spores. Spots also appear on the plants’ stems"

Coin-sized? No. Black or dark green lesions on the leaves?Yes. Surrounded by halos of white spores?No. Spots on the stems? No.

I think what I'm going to do is get a healthly leaf tomorrow morning and spray it with ammonia and keep a close watch on the plant too. And pray.