For the first year of life, the vast majority of baby's nutrition is from breastmilk/formula. When beginning solids, they are for experimentation only, gradually providing more and more nutrition. Pushing more solids at this point would only NEGATIVELY impact his nutritional intake, and block the absorption of what he does get from his formula.
Putting another scoop of powder in his formula isn't nutritionally balanced either. And in two weeks, he would've gained an ounce or two regardless.
Has his percentile dropped, or has he remained consistent? Why is your doctor concerned? Low percentage does not equate unhealthy, or a need to bulk up.
And lastly, it's odd that this exact scenario was posted earlier with a female baby.