Parsley Problem

[Lionitus]

Finally, I have something to post somewhere other than Pets! I don't have my own yard again yet as we're still renting a house in our new town but with any luck I'll have a yard in the next two months.

Anyways, I have a parsley question I'm hoping someone can help me with. I have curly leaf and flat leaf parsley growing in pots. For some reason their leaves start to yellow and within a day or two they turn brown and fall off. What is wrong? I have them in good draining potting soil, I check their water carefully and they are in full sun. I'm wondering if here in my zone 7b climate if they aren't getting sunburned? Already the sun is very hot here. Any ideas what I could be doing wrong?

Thanks and happy spring!
Lionitus