What happened to my negs?

I developed 3 rolls of Neopan 400 and each one had the same results.Here's a list of the variables:
-the film was shot last winter (just found it in my fridge)
-camera,a pentax MX
-tank & reels were Patterson (plastic)
-developer HC-110 50:1 for 8 minutes

I can't figure out if it's the camera's fault or the idiot in charge of the processing (me).

Well, I can't say for sure but to me it seems like a light leak either at the take-up-end of the camera back, or through the cartridge opening.
Weird that it comes at the same place on each frame.

Gr.

It does look like fogging. You say every frame of every roll has this problem? Were they all developed in one tank together? Some frames are worse than others, so I'm thinking this is happening in the camera, with the amount of time between shots determining how bad the problem is. I had a leaky shutter curtain once in a Leica M3 (different defect, but still an analogy), and the defect was worse when the time between shots was longer. In your example, the middle one is obviously the worst, so maybe more time was spent between that one and the next (or between the one before and that one - you don't know if the leak is before or after the frame that is behind the lens). Maybe this has something to do with the camera back seal, either the hinge side or the lock side.

A sticky second curtain of a focal plane shutter?

I had the same problem with a back of mine, it was a minor leak on an edge and as the film sat in that particular location, it exposed the light and ruined the film. I have found that leaks centering around the top/bottom of the film suggest light leakage either in the cartridge or developing tank while leaks across the centers of multiple negatives suggest leaks in the camera. I bought a sealing kit from eBay and it fixed the problem. I'd recommend changing the sealing on all edges of the camera. This is a picture of my problem, which looks very similar to yours.

Thanks folks!
I made the stupid mistake of mixing up my Pentax MX's.One was to resealed,the other looks like a beater but is tack sharp.I looked at the light seals last night.Non existent.Knob mistake.