Slight discomfort in the rotor cuff

Quick questions. I read a lot about how to deal with arm discomfort after games, like running the day after and icing it. I never used to get a sore arm in high school but now that i am 30 my shoulder is a little sore a few days after i throw at about 90% power and 75-85 pitches. By sore i mean i can feel some slight discomfort in my rotor cuff the next day when i move my arm slowly to the high cock position and then forward slowly to a release position while i have my arm and shoulder tensed up. Is this what everyone is referring to? if so is this normal or should i chill out a bit and get my shoulder in better shape before throwing again?