Creeping phlox require good drainage more than anything else. If you planted them during hot dry weather they may have perished from heat and lack of water. When flowers begin to fail some gardeners over water and fertilize them with chemicals. Not good either. Creeping phlox like humus rich fertile soil. Keep it moist but not sodden. I would give them a soil drench of fish and kelp fertilzer, such as Neptune's Harvest, in spring, and that's it. A light mulch of composted bark will help to keep the soil moist, but keep it away from the plants stems. If you have heavy clay add gravel to the soil for better drainage. Best and Happy Yardening, Nancy.