They won't toughen up. I planted a chamomile lawn when I first moved into this place - and it lasted less than a day. The sun cooked it! You'll have to move it to a shadier, cooler place.

thank you very much for your response. i've had a nice new place in mind, just in case that was the verdict.

Sarah, I don't which zone you are in, but here in zone 5, my established chamomile takes full sun just fine. New transplants are very tender and need extra coddling when first planted. Give them an extra drink of water. You say you have other chamomile in full sun? These new plants should do okay then.

It takes full sun for me here in Sacramento... subdesert conditions. I am thinking that you are overwatering it... apparently it can develop an 'underwatered' look when you overwater it.

hmmm.... now i just need to figure out what i'm doing wrong! i don't believe i'm over watering... but i'm sure it possible. i'll try cutting back on that.
oh, btw, i'm zone 7. appalachian foothills in northeast alabama.
thank you all for your advice.