Dill and celantro are annual herbs that do not care for hot weather. In response to it they try to complete their life cycle by going to seed and these remain dormant until more favorable conditions prevail. They may very well have dropped seeds that will germinate for you later on. If you decide to put in more dill and cilantro or to start some plants from seed, put them in a partly shaded place where the soil remains damp and cool with plenty of organic mulch. You will get much better crops during the cooler times of the year.