What Causes Painful Leg And Foot Cramps?

I am 64 yars old 6' 180 lbs. I served in Viet Nam in 1968-69 and was exposed to agent orange. Currently I am on high blood pressure medicine. I wear compression hose at times I have developed leg varicose veins over the last 15 years and was treated for a blood clot in my upper left leg 10 years ago. I sometimes experience painful leg or foot cramps severe enough to wake me at night, they last up to an intense 5 minutes. Currently, I am at the point where the blood is sometimes pooling in my left foot and ankle releasing enzymes that are affecting my skin and cause intense itching.
Before I go through the involved process of submitting a VA claim. I am attempting to get an impartial opinion on whether this could have been caused or is part of a reaction to agent orange. exposure