Hopefully, you added about 1/4 or 1/8 tsp of grape tannin so that's not why it's brown. I've never seen it in strawberry wine, but I've seen some wines get really ugly. (Look at my banana wine recipe, there is a picture of the must in another post and it's hideously gray). What I think must have happened is the pectic enzyme is already working. Pectic enzyme breaks down the cell walls of fruit, so maybe that's why? I don't know, but that's my best guess.