Hi, I also have 2 percs. I bought them both a week apart. When I added the second, which was smaller than the first, they got along pretty well right away. Then after a few days, I notice that the bigger one, the first clown I got, was definately the dominant one. I see some minor quarreling between the two, but this only happens at feeding time. The bigger one always eats first. The smaller one would stay in the back. I feed my clowns frozen brine shrimps (they love this stuff)...when I feed..I make sure that some shrimps drifts away from the big clown and heads towards the smaller clown. The smaller one would pick off the drifting shrimps...this way they both get to eat.
I think the main problem is your food..my clowns despise flake food. They'll take it in their mouth but then spits it right out. Try frozen brine shrimp, they'll love you for it