Weird Walleye?

So here I am fishing the same bay I previously fished the week before and limited out, and now I'm having trouble bringing in a single fish. so finally I decided to throw out a slip bobber with a leech 6 feet down and right away BOOM! There's  a 20" walleye caught and released (as I only keep what I eat and the slot fish are better than anything) so I'm thinking "sweet here's the fish" put it back out there and there's another 21" caught and released. I finished off that day on Shebandowan with at least a 20+ fish day before I left I trolled over that spot to mark it and it was 32 feet of water. Now I'm thinking why are these fish that have been stuck to the bottom all year coming up from 32 feet to grab a leech suspended 6 feet down? The next day I went back there and threw the bobber again and couldn't interest a fish to bite.  I put on a bottom bouncer with a spinner worm harness and dragged it across the bottom. Right away there was a fish. I then went on to catch ten more before I had my two in the live well and headed back to camp with more questions in my head. I don't know why the fish would of been suspended that day or why they came up 28 feet to grab a leech but its a first for me.