I Second this. Shutter speed too slow for hand held at 300mm.
Hi Lee, assuming you didnt use a tripod and seeing you say they were at 300mm, my guess is you have a bit of camera shake affecting your samples.
Being a new lens and perhaps not being used to the extra weight and length, I think 1/125 and 1/200sec exposure is a bit brave.
Try 1/500th sec and work up from there, light permitting of course.