You should read up on cortisol circadian rhythm. After about 2 weeks prednisone is making your cortisol. Your body has stopped producing it. Thats why it takes a taper to get off prednisone. Your body does not produce cortisol just in the morning. It produces it to a circadian rhythm or when needed for stress response and other daily requirements. Your morning requirements are the highest. You feel the most pain during that time. It takes the prednisone several hours to start working. Plus the fact your requirements start decreasing by mid day. You could try a split dose or taking your prednisone early in the morning. The only drawback is it can affect your sleep. I think everything sounds perfectly normal.