Two things at play here.
One is incomplete mixing of the priming solution.
Two is that you may have different yeast concentrations, slightly different temps, etc, in different bottles. You are dealing with living organisms, after all; they carb properly when they carb properly.
Give them some time, and odds are, it will evenout (more or less).
Do note that you shouldn't have any bottles that form until the beer is gone, though - that sounds like a possible infection.
- blogging about making my own beer and raising a lot of kids.
Check out the priming sugar calculator
and the beer calorie calculator
Fermenting: American brown ale
Bottled: big Irish red ale, Thundersmoke brown ale (Yorkshire brown), Belgian golden strong ale, imperial nut brown ale