In full sun, in the middle of a large patch of rocks, I have....

Variegated Wiegela
Rhododendron
Holly
spiraea
euonymous (green and white)

I don't have the latin names for any of these. We put them in several years ago when my idea of gardening was to plunk something in dirt any-old-where and maybe water it every once in awhile. Needless to say, these are not thriving.

My yard is mostly full sun, but I do have a few spots that have shade for part of the day. What can I do to help these poor victims of my ignorance?

I can post a picture if you want, but I am basically looking for simple suggestions, and a way to prioritize what to fix- which to move first, and to what kind of area, etc. I know it's imprecise, but it will be a start.

One way to determine sufficient water is to plan to irrigate any time you don't get 1 inch rain in 10 days (if they are baby plants, figure 1" per week). Water slowly to give it a chance to sink in rather than run off. Shrubblers, soaker hose, gardeners-IV bags, even a tiny hole in the bottom of a large bucket are any and all better than turning the hose on full-blast.

The rhodie will do best in part-shade and a soil that is full of humus and fairly well-drained. It will also probably sulk for a year (they don't like being moved) but then take off to reward you with a gorgeous display of blossoms.