Why do my lower calves seize up so much when I run now

tight hip flexors / forward pelvic tilt, insufficient warm up + cool down, electrolyte deficiency are probably top 3 possibilities

this is a good routine (video is crazy long but can skip through to check out the movements)

this is a good routine (video is crazy long but can skip through to check out the movements) https://www.youtube.com/watch?v=nLdjvFzjl2w

Honestly king just more core work, and some Cali lower back exercises like front lever raises