If you have a tower the lines are probably getting warm in the tower and the first glass will be foamy until the lines cool down or you may need a bit more line to equalize the pressure.
I have roughly the same setup you describe with a two tap tower and I get a half a glass of foam with the first glass. I just don't worry about it. Also you may be over carbed which will balance out over time under the 8-10 psi. I usually force at 30 psi at room temp and only 15-20 when the beer is cold.