I think I've solved my problem. The dark marks were from over-agitation. Basically with two 120 reels in there there is still enough room for them to move around when I aggitate leading the bottom reel to get too much aggitation.(posted 8292 days ago)I ran a test with two reels and a 35mm reel in there to hold them tight. I filled the tank up to the top and developed normally. No staining.
You learn something new every day....