Change the scale of the skydomes. Click itand press CTRL+B or CTRL+SHIFT+B (Not at my desktop so I can't be sure) the scale is at the very bottom of the dropdown list. The biggest scale I've used on it is around 30 and the textures still seem to be fine. Also if you're planning to do a very drawn back perspective shot and the skydome is really far it could get affected by the depth of field quality on the atmosphere tab. To make sure this doesn't happen go to the atmosphere tab, then go to varia tick the depth of field box that says "near-only" or something like that.
I can't actually target mine. Click+Drag doesn't pick it. I doubt it, but would it be listed in the items or something else?