I can relay 2 stories of something similar. First, is the story of the Father to my Albino. The guy that I bought my Albino from has an Albino (duh) that only eats about 4 times a year. He doesn't gain weight at all. Now he is adult at somewhere around 1000 grams, so a bit different. Sometimes they just don't want alot to eat. The second story involves a Het Albino female many years ago (when it was a very valuable animal in a collection) that would not eat unless you put her in a bag and drove her around in the car for about 30 minutes to an hour. Then put her back in her tub, and she would eat. I know this sounds strange, but it is a true story.

With all of that said, I can relay a couple of stories from my collection.
1. My original Het Pied male got to 1200 grams in his first year, but didn't breed until his third winter at 1500 grams.
2. I have some 04 Normal girls that are about 900-1000 grams, and barely ever eat (they will get bred in the upcoming season).
3. I have a 04 Pied girl that weighed 1100 grams earlier this year, until I found out that she liked African Soft Furs.

All that was meant to show that theses are individual animals, and they can be very different from each other or the norm. You may want to look into getting him an ASF if at all possible, or (I know this is not always seen as a good thing) leave a small live rat in overnight. I have used the live overnight trick before to get stubborn eaters to eat again. In summary, I would say that if your guy is not sick or losing weight, he may not want to eat alot, or the husbandry needs a slight tweak somewhere. The last thing that just came to mind, is to try and move his enclosure somewhere else (i.e. higher or lower in the room, which will change his ambient temp, or closer or further from a window, which may change his lighting. Sometimes a move can be good to spur a stubborn eater.

I hope some of that helps or gives a better understanding of the uniqueness of these animals.