Brooks B17 saddle tension?
Leather saddles start to sag unless you add tension due to the leather stretching over time. How much tension depends on your body weight and how slack the saddle has become. Try adding enough tension that the saddle feels somewhat taught, but you can still depress the center of the saddle a bit with your thumbs. Ride it then add adjust the tension 1/2 turn at a time until you find the sweet spot. 

Note that too much tension can cause the leather to tear starting at the rivets. So watch the leather around the rivets, you can usually see signs in the leather before it tears, let off some tension in this case.

Brooks leather saddles are suspended at two points, the front and back. What you are seeing is the leather bending over the forward contact point, likely caused by the sagging from too little tension.