I have finally developed a great formula for a naturally leavened sourdough. They are slow rising, but they come up very nicely. The problem is that when I slash them, they deflate. I tried to make a more shallow slash, but then I don't get a nice looking slash after final baking. Maybe I am proofing too long I guess, but I don;t get the nice open holed texture I like if I don't proof it to that point. I am using a very sharp lame each time so I know that isnt the problem either. Any ideas?