nice race. i used to have the same soreness/tightness issues occasionally after doing sprint work like that, but I always preferred to feel good for those sprints and then just suck it up for the workout the next day rather than feel tired/sore before the sprints.
Whatever you are doing seems to be working, so I'd just stick with it. I wouldn't go out any faster or slower through 600 next time, just do basically the same thing and maybe you won't die quiet as much the last 100. Good luck.