Has anyone else noticed lens resolution issues with the K-5?

I only ask, as some lenses I have have been perfectly fine with the DS/K10D/K20D, but with the K-5 images are softer or the AF cannot cope etc. Ironically my Prime lenses are still stunning!

Specifically (so far)
Sigma 55-200 DC F4-5.6 (Budget lens, so not surprising)
Sigma 170-500 DG APO - Can't keep up with the AF in certain circumstances
DA 16-45 F4 - Sharpness trail-off to the edges, even at F8

The sigma 24-70mm EX F2.8 and DA* 50-135mm are more than a match for the K-5 though.

I've not noticed any such difference between my old GX20 and K5.

Well I never thought I would see that said about a Pentax camera.

Mine all seem fine.

A sensor that outresolves all your lenses doesn't sound much of a problem to me!

My Siggy 24-70 is great now, with some adjustment. The sharpening I need in GIMP is a lot less with the K5 - and that's also with MF

Bret