I know this is a very late reply, but maybe it will help for next year! I have a couple of ideas. If those are petunias, you must deadhead them-that is, pinch off the flowers when they start to wilt/fade. If you don't, the plant will go to seed rather than keep blooming. I tend to water my pots every morning until the water runs out the bottom unless it rained during the night or if I have shaded pots. I live outside DC, so summers are hot and humid. Other conditions may require slightly less watering. You have to walk a fine line between overwatering (worse than underwatering) and letting your plants get too dry. Also, it is possible to use too much fertilizer. You will burn the roots if you do that, so maybe add the Miracle-Gro every third or fourth watering or use the miracle-gro potting soil and don't worry about the liquid form.

It looks as if you have pretty good light. Petunias like full sun-at least six hours, but I have been able to get by with about five hours of sun on our deck.