Windowsill Herbs

I purchased your Indoor Windowsill Collection seeds recently and am having limited success in growing them. The plants are about two months old now and are in terra cotta pots on ledges of a south-facing window with no filtering of sunlight. I allow them to almost completely dry out before watering. The oregano is the only one which appears healthy. The others, while growing, are a rather pale green and do not seem as sturdy as I might expect of plants their size. Additionally, I've pinched a lot of browned foliage off the dill, basil and parsley.
Can you give any suggestions on the growing conditions needed to make these plants thrive? I am expecting a delivery of an additional 9 or so plants from you shortly and hoped to grow most of them indoors under the same conditions and train them into topiaries. I hope you can provide some insight as to what I might be doing wrong.

Since oregano is doing well while the rest are not, your problem could be the pH of the soil. Try adding a top dressing of peat moss and see if that helps.
Also, if your south window is not unobstructed by other buildings or trees, your plants might not be getting enough light and their lighting should be supplemented with some flourescent tubes.
Are you sure that you have not let the plants dry out too much, thereby killing a lot of their roots and giving them a terrific set back? If that might be the case try watering a bit more frequently.