Is B6 and Magnesium good for blood pressure?

Not a treatment. Vitamin B6 and magnesium are essential nutrients, generally found in adequate amounts in mixed diet. However, neither of these is a treatment for high blood pressure.
Wish you good health! - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form.
Practice safe sex, if you have sex.