It's hard to tell without looking at the image as fuzzy blobs could mean a lot of things. I think cooling and seeing will have effect, but you will only see it at high mag. Low mag should be OK, if this is the problem.
Bad collimation will make the image look skewed in one direction or the other, when defocusing you will notice it more.
Coma you will definitely have and I'm afraid to say that there is not really a cure is such a short focal length scope, unless you get youself a set of Panoptics.
You will see the coma around the edge of field, maybe even all the way in, depending on the eyepieces you have.
If the bright stars look much bigger than the faint ones, well, umm...
Don't do what I did and go and look through a $15000 5" Takahashi APO. The brightest stars will look the same size as the faint ones and you will never be able to turn back and end up selling your newt like me and probably die a very poor old man with only one scope (But at least you will have lots of friends... Hi Mark!!!).
So do what Dave P. said.
