Weird Background noise on images after smush installation

Apologies for not putting this in the smush thread, but i have uninstalled it and it wouldn't let me post without selecting a plug-in and since it wasn't there, i couldn't select it.

I had smush installed as an experiment, and have since taken it out as the images now have a weird shadowy grey noise/colour in their background instead of just white. After removing it, images uploaded after removal that have not been smushed are still coming through with a weird background . If i link them directly from a url after uploading via ftp, they are fine, but if I upload through the media manager, they have this strange background on.
It is only faint, more like an almost transparent noise in the background. In the first image you can see it, in the second, it was linked directly from a url and the clean white is as it should be.

This never happened before smush went in, and nothing i seem to do now can get the proper images working again if the upload manager is used.

Any guidance greatly appreciated