You're not doing anything wrong...they simply aren't ready yet.
Uneven carbonation is simply a matter of not enough time. The sugar solution integrates itself pretty well when you rack (despite what many new brewers may believe)
BUT, just a tiny difference in temps between bottles in storage can affect the yeasties, speed them up or slow them down. Like if you store them in a closet against a warm wall, the beers closest to the heat source may be a tad warmer than those further way, so thy may carb/condition at slightly different rates. I usually store a batch in 2 seperate locations in my loft 1 case in my bedroom which is a little warmer, and the other in the closet in the lving room, which being in a larger space is a tad cooler, at least according to the thermostat next to that closet. It can be 5-10 degrees warmer in my bedroom. So I usually start with that case at three weeks. Giving the other half a little more time.
Each little bottle is a seperate microcosm, so they will react slightly different to each other. But usually they all will balance out given enough time.
But really with time all the bottles in a batch will carb up...
The
3 weeks at 70 degrees, that that we recommend is the
minimum time it takes for average gravity beers to carbonate and condition. Higher grav beers take longer.
Stouts and porters have taken me between 6 and 8 weeks to carb up..I have a 1.090 Belgian strong that took
three months to carb up.
I explain this and more, in my blog, here
Revvy's Blog, Of Patience and Bottle Conditioning.
Uneven carbonation is simply a matter of not enough time
. The sugar solution integrates itself pretty well when you rack (despite what many new brewers may believe)
If a beer isn't carbed by "x number of weeks" you just have to give them ore time. If you added your sugar, then the beer will carb up eventually, it's really a foolroof process. All beers will carb up eventually. A lot of new brewers think they have to "troubleshoot" a bottling issue, when there really is none, the beer knows how to carb itself. In fact if you run beersmiths carbing calculator, some lower grav beers don't even require additional sugar to reach their minimum level of carbonation. Just time.