I think you need to alternate your exercise days. Working out twice a day and that too once in the morning and again in the evening doesn't give your body much time to recoup from the workout. If possible, try alternate days where M, W and F you do the 30D shred and Sun, Tues, Thur you do the evening walks. That gives your body time to recoup and you get a Sat off for the muscles to recover.
Good luck!
