When I first start to play my D chanter, it plays easily and crisply.
But after about 5 minutes of playing I begin having a difficult time hitting
a clean B and C# in the first octive. It is very sloppy going from back D
to C# or B and they seem to sound weak. This problem developed a couple of months ago. I have tried to pay close attention to finger position, but this problem has been frustrating. I live in a winter climate,
but I have a humidifier in the case and in the room I play in. Is this just
my lack of good technique or does anyone have other suggestions. Thanks
I wouldn’t be too concerned as of yet, it is still winterish in the cooler climes and this will affect your reeds behavior.
Naughty, Naughty… Naughty reed 
I would suggest that you are holding the chanter too tightly. The harder you squeeze the chanter, the less blood gets into your fingers, and the fingers then become stiff and clumsy.
Rather than work on hitting the notes, I would suggest you practise holding the chanter as lightly as possible. You only need to cover the holes. You do not need to squeeze the crap out of the chanter.
Use your shoulders and arms for strength. Keep your wrists and fingers soft and supple. Practise this first. Then worry about playing notes afterwards.
djm