I used to get leg cramps after especially long bouts of violent exercise, and eventually pinned it down to being most likely caused by dehydration. Wouldn't know if that's the reason for yours but may be worth taking some water with you and seeing if that makes a difference.
It could be that you need to stretch a bit more, or sooner after your run. If your muscles in your legs are tight, you might need loosening up a litte Good luck with week 4
I've always had cramps in my lower legs and feet, not necessarily related to exercise. The main thing for me is keeping them warm enough, so I always wear long socks in winter, and drinking enough water and taking magnesium supplements also seems to help. I sometimes get cramp down the inside and bottom of my foot when I'm running and the thing that really helps that (more than stretching) is simple ankle rolls (sit or lie with your foot in the air and roll the ankle a few times each way). And then heat. Don't know if this'll work for you, but it's the best solution I've found for me.
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