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I wonder if you have tried (as Bob suggests) your lowest power eyepiece with these DSO's.
For example, M8 is a big object, and quite bright: your C925 should eat it, but it is over a degree in size (around 90x40 arc minutes), so you really need to use low power to start with. The stock Celestron 40mm eyepiece (e.g.: the one that came with my C800) has only a 43 degree apov. With the C925 this will give you 58x, and around 41' true FOV: which is only about 1/2 the full size of M8. This means you will need to pan around to see the whole object in your scope: so you might have been looking at a part of it, and not realised!
M20 is about 28 arc minutes, so a fair % of your true FOV at low power, and M22 is around 32 arc minutes... so really need to use at least the 40mm plossl for these objects to start with as well.
With a low power eyepiece you should be able to see the lanes in M20 (although don't expect any colour!), and resolve stars in M22 quite happily, so I am wondering whether your collimation is out or whether your finder is properly lined up with the scope? Check your finder in the day-time with (say) the top of a distance pole.
Good luck!
Dean
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