I suffer from very stiff muscles after exercise, it seems correlated with stress. other than stretching, is there any diet/lifestyle i can do to minimize this, please?

Perhaps: Make sure you are well hydrated when you exercise. Your physician might want to check to make sure you have a normal potassium, magnesium, calcium, and vitamin d level. Also, there are some reports that having caffeine just prior to exercise might result in less muscle cramps afterward. In general, though, some muscle pains and stiffness are expected after vigorous exercise.