This looks like uneven development, definitely not a light leak. I've had a light leak in my Hasselblad once- it looked completely different.
In 2008, when I picked up medium format again after too long a hiatus, my first film or films (I don't remember how long the problem persisted) showed the exact same unevenness as your example photo(s). After some reading, thinking and trying I got rid of it.
There is a personal element to solving this problem (because not one workflow is the same between different people/equipment), but I can say for myself that sticking to my own rules (), as set out in my previous post in this thread, simply works. Maybe you can take these and other people's advice on this issue as a starting point for finding your own consistently successful developing method.
I am a bit puzzled as to why there isn't more talk about this issue floating around on the web. Surely many starters in 120 must run into this or some similar agitation problem. Well, maybe there is talk, but not so much a unanimous solution. This again may have to do with everybody working in their own particular way. Too many variables, in other words.
When I was confronted with this problem I was somewhat dismayed that none of the 'official' sources (Ilford, Kodak, Way Beyond Monochrome, etc.) take it on in a practical manner. If it is mentioned at all, then most sources suffice to say something like "uneven development is most likely related to improper agitation, agitate sufficiently, most importantly at the start of the process". Well, maybe it is properly dealt with (i.e. practical and in detail) somewhere. If somebody knows a good source please let us know.
It would be a pity that beginners turn away from 120 because of such a trivial problem.
I hope you get this sorted out Jeff. No need to explain to me how annoying and frustrating it can be.
"There's no trick to it, it's just a simple trick!" (The Simpsons- Bart's Inner Child, 1993.)