White Marks on Laundry?

Someone put wet clothes in the hamper and by the time I found it, everything smelled awful. I usually put baking soda in the washer, anyhow, so I put in extra to kill the extra bad smell. When I took the clothes out of the dryer, I noticed that a few of the darker t-shirts looked like they had white sweat marks. Two shirts were brand new so I'm thinking it was the baking soda. I washed them again, but the white marks are still there. Can anyone help?