Oregano Dying in Southern California, USA

I purchased some nice oregano plants from you which grew quite large. I have them in a clay pot. Suddenly their leaves started during yellow, then brown. One plant died off completely already, the other is 1/2 dead. We have high temps here and lots of light (Southern California, USA). Any ideas?
PS: All your plants and seeds have been great.

There could be two reasons for the ailing of the plants. You did not say which variety of oregano you purchased and not all varieties can take extreme heat. Southern California can be in zone 9 or all the way to 11 or tropical. Check the zone rating of the oreganos you purchased and if the zone you live in is too hot, then the plants should be kept in a pot and the pot placed in a sunny window in an air-conditioned room for the summer. Outside plants can really suffer from drought. Most oreganos come from the Mediterranean and never dry out completely because of underground water and high humidity at night. So keep the plants watered during droughts . Once the roots have turned to hay, it is hard to save the plant.