Are they brown and soft, or brown and crispy?

It's been pretty hot where I am, and my regular plantings have been quite thirsty. My new transplants are going through shock, even though I did them early in the season, and don't seem to be taking up the water that they should be.

Try covering them with some netting so the sun is not scorching them, and water, water, water.

Brown soft leaves are often a sign of overwatering. Maybe you have been too diligent on the watering. The soil needs to dry out a bit between waterings.

If you are concerned about fungus, take a leaf sample back to the nursury and have them take a look at it to identify a possible fungus problem. Can you post a picture here?