Based on your location, it may be to late for cilantro because of the heat. Cilantro is extremely sensitive to warm weather. It needs to be sown in your area immediately after danger of frost. You are in USDA Zone 7B
so ideally your cilantro should have been planted April 7th.
Heat causes cilantro to bolt (go to seed) very quickly. Since cilantro is short lived anyway, heat doesn't help.
If you still want to try growing it, try moving it to a bright yet fully shaded area. Or an area which gets eary morning sun and is in shade the rest of the day.
Herbs don't like to be fertilized. They actually prefer soils with less nutrients, just make sure it's well drained.
Try sowing slow bolting varieties, if you need sources, let me know.
"Cultivars to consider are `Santo,' `Leisure,' `Jantar,' and 'Slo-Bolt" all of which are slow-bolting and have been bred specifically for foliage production rather than seed."
"Coriander, a cool season crop, is easy to grow as a culinary herb and is most suited to fertile loam soils...
One of the major problems in producing cilantro is premature flowering. Bolting becomes acute as the days get hotter and longer. A number of seed companies now offer slow-to-bolt (long-standing) cultivars. There are significant differences among coriander cultivars regarding the response to premature flowering, and while some are less susceptible, none are totally unresponsive to high temperatures and long days (Simon et al. 1989). Thus, cilantro is planted as a spring, early summer, or fall crop."
For more info, lookhere