Answer: If the sun exposure, water and fertilizer are the same, then I would suspect some soil problem. I'd remove the plants, spread 3-4 inches of organic matter over the soil and dig it in to a depth of about 8 inches. This will improve the tilth of the soil which will help it drain quickly yet hold just the right amount of moisture. Since snapdragons grew there before, the soil should be reasonably good enough for petunias. Good luck with your next planting!
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