[cypher]

That sounds good, I wouldn't worry about the fat being high, it is quite difficult to keep it low without compromising on other things, that amount should be fine.
Protein is fine for the two younger hams but by 18 months you may want to begin thinking about reducing it very slightly, it's not about how active your ham is as much as it's to do with kidney function which can suffer from too much protein as they begin to get older.
If you do the change over slowly then it shouldn't matter if there is a fairly big change in some of the macronutrients.
I know what you mean about doing the maths lol! I've made small changes to my mix several times since I began & having to recalculate each time is a bit daunting!