I would suggest that you add in correct stretches for the flexor hallucis longus and flexor ditorum longus muscles, these are muscles that are deep to the calf muscles and you use them to press the pads of your toes downwards. To stretch these muscles you do the same as a calf muscle stretch but firt place a phone book or block in front of your toes so that your toes are at 90 degrees to your foot.

I would also add very regular deep massage to this area either yourself or by a sports masseur.

Alternate ideas would be to see a sports physician to test for posterior compartment syndrome. This is where there is a restriction of the venous blood flow out of the muscle compartment after exercise thus high pressure. There is a pressure test that can be done to diagnose this condition.

It would be great to hear back if any of these ideas are helpful