It sound like the plants are collapsing for some reason. If this is happening on most or all of the plants, I would suggest pulling one or two up to look at the roots. There are many things that can contribute to plant collapse. I am suspecting that some thing affecting the root in a large area (front yard) is affecting the plant - some guesses include too much water (or too little water), and too much fertilizer.
It would be helpful if you are able to submit photograph of your plant showing the symptoms.