If the leaves in direct contact with the sun turn yellow, including the leaf veins, it may be too much sun. Or the soil may be alkaline (the leaves turn yellow except for the leaf veins which remain dark green). A few yellow leaves in the Summer might suggest heat or watering issues/stress but the whole shrub would be rare.

The whole plant is in direct sun for most of the day. I don't know the soil ph but I'm guessing it's acidic enough. I have blueberries and arborvitae back there that are both doing well. I've had hydrangeas in my last house that would wilt when they needed water. These aren't even wilting so I'm thinking it's not a watering issue. Do Little Lambs just have lighter leaves?

Not as yellow as In the picture but you could try a chair or something else to provide temp shade since it is their first summer. Down here, paniculatas cannot tolerate much sun so I give them morning sun only or bright shade.

This far north, full sun is fine. It isn't for Luis. You are somewhere in between. For now while they establish roots, I would give them some extra shade from a temporary screen or a lawn chair or something similar. The growing conditions may be quite different from those where they were previously. If they do the same thing next year after having some time to get established, I would plan to move them to where they will get some shade in at least the hottest part of the day, or alternatively, plant something that will give them some shade. I would also actually stick my finger a few inches into the soil in the original root ball and in the surrounding soil to be sure there is adequate moisture there.

Little Lamb leaves get notoriously yellow anyhow. I used this trait combined with the fact that the stems have a ruddy color to determine that a Limelight I bought was indeed a Little Lamb. Not the greatest hydrangea either way.

And a reminder: DON'T water unless the stems & leaves are drooping. This will increase yellowing.

Thank you so much for all of your comments! I think this spot may be too sunny for hydrangeas. They get no relief...at all. Springwood_gardens, it sounds like you're not a fan of this hydrangea anyway. I was thinking of moving them but maybe I should just remove them and try a different one altogether. I do NOT like yellow leaves. Which hydrangea do you recommend?

One more thing...I meant to include some close up pics!

If I had to recommend any replacement for those It'd be Phantom or Sweet Summer. SS'd be closer to your ideal size.

Either way, maybe try giving your LL's a couple years to see what they do. All in all, they don't seem to grow vigorously enough for my tastes.

Here's an in-depth discussion that was started back around when LL came out:

http://forums.gardenweb.com/discussions/1981883/hydrangea-little-lamb-in-full-sun

Thanks springwood_gardens! I should've researched LL more before ordering it. If it were that great of a hydrangea, it would be more common, I think!