1. You training is geared towards strength, not size so the growth stimulus is reduced greatly.
2. You probably are not eating enough to maintain the muscle you have gained (since you did do a PH cycle).
3. You're sprint training isn't helping AT ALL.
This goes to show that heavy weight does not equal size increases. Its tough to be a bodybuilder (or at least try to look like one) and be an athlete in which speed, endurance and strenght are the focus withouth being blessed (the majority of professional DB's and LB's.
You could try to incorporate more size training but at this point you really have to pick a goal. It will be REALLY tough to maintain the weight you were during your PH cycle while still focusing on strenght training. What you could try to do is focus all your compund exercise on strenght training but everything else towards myofibrillar hypertrophy (reps from 6-10 w/ moderate weight)