Now here's a tree fungus I shot handheld with the same camera and lens at f5.6 ISO500 and 60mm. It's not as sharp as LunaZ's sunflower but still it's pretty sharp. Lots of detail. My sunflowers were shot handheld while sitting in the car looking out the window, I think. I had the tripod out that day but I don't think I used it on the sunflowers now that I think about it.
I think maybe the high f-stop on the sunflowers and the fact that they're backlighted took away some detail. Anybody else have an idea what's going on?