I just recently bottled my 4th and 5th batches and it seems that I've got some under-carbed bottles. I cold-crashed both prior to bottling and lowered the amount of priming sugar (dextrose) accordingly, but I'm wondering where I went wrong. I created simple sugar and allowed it to cool to room temp or a little above before adding it to my bottling bucket and then siphoning the beer into said bucket. In the past, I have done this and allowed the natural circulation of the beer from the siphon mix the priming solution. However, I'm thinking that the colder temps may have prevented the solution from mixing very thoroughly. I like to use a few PET plastic bottles in order to judge the levels of carbonation, and it's evident that some are better than others. In the future, should I allow my beer to warm back up after crashing or should I be more intentional about mixing the priming solution with the beer (without aerating it too much)?