What is Magic's current weight? How much is he eating per day? Is the hay and timothy pellets being weighed? Total weight being fed (hay + pellets) either 2% of ideal or 1.5% of current - whichever is greater? If he's off the Purina and Blue Seal can you indicate that in your CH?
If he's down to a normal weight and eating an acceptable amount you may want to consider using Invokana for him.