Matt, there's a chance you've got a duff one but unlikely.
A couple of things that could be affecting your ability to focus...
- poor atmospheric conditions (seeing)...if you attempt to focus on a bright star, does it appear to be be pulsing irregularly around the centre, almost as if it's on fire?
- thermal issues with your ota - give your scope adequate time to cool down to ambient temperature. You can see thermal currents in your scope as a kind of hazy view
- collimation being far out? I'm not certain about this one. If your collimation is close but still a little off you will get flares on a bright star or Jupiter for example. Try dialling out the focus so you see a donut. Where is the dark hole located relative the the bright donut?
A few smudges on the optical surfaces shouldn't affect the image to this effect. The primary mirror moves when you turn the focuser and cannot be collimated, it's just the secondary with a SCT.
What eyepiece were you using when you see the symptoms as described?