Two weeks ago, you talked about wanting to do a chest specialization. Did you do that? If so, what were the results (strength and measurements)?
What's your current height, weight, and general fat level (chubby, lean, "skinny fat", etc.)?
Overall, I think the general idea you're trying to work with (a full leg day, a quad day, and a ham day) could be something, but I don't know why you're using the same handful of movements on all the days. I'm also not sure your "quad day" has a significant quad emphasis. And calves. If you're doing a leg focus, train calves.
Lastly, there's no reason to only be doing 3-4x10-12, even with some slow negatives or pauses. If you're attacking the legs, especially in multiple sessions per week, hit 'em with everything - some heavier lower rep stuff, moderate work with the negatives, and crazy-burn high rep sets.
You might be better off considering this 4-week plan with 3 leg days and an upper body day. John Meadows stuff is always great, if you're up for it. These are some Mountain Dog routines to try.
Something else to remember with any specialization program, especially legs, is that you're going to want to crank up your calories and not skimp on protein, carbs, or good fats. If your bodyweight doesn't go up week to week, you're hamstringing your progress. Horrible pun intended.