Thanks for all the comments. However, after toying with this a bit more I am know suspicious I have a software bug. By adding a bit of movement to the still clips, a red render bar “sometimes” appears…hit and miss. When I get the opportunity to render the clip, the picture quality smartens up.
If I recall, in previous versions of FCP, any time I dropped a photo clip into the timeline, a red render bar would appear. I just upgraded to FCP Studio, and wondered why the render bar was light grey. If I play with the clip a bit by adding movement, or colour correction, sometimes I can then render the clip, sometimes not.
Sometimes if I change the time line playback settings back & forth, that will prompt a red render bar, but only sometimes. There is no logic to this glitch.