Answer: Snapdragons really enjoy growing and flowering when the weather is cool (spring and fall) but many varieties will flower during the heat of summer. I suspect your snaps are reluctant to bloom when it's hot. Try planting in late winter for spring blooms, then remove the plants and plant fresh plants in the early fall for fall and winter blooms.
Snapdragons are susceptible to rust (the spots you find on the leaves). Rust is a fungus and improving air circulation around your plants, watering the soil rather than the foliage, and removing any leaves with rust spots will help prevent the spread of the disease. I have good success with reblooming when I cut the flower spikes off the plants when there are only 2-3 unopened flower buds at the very tip. Cutting the flowering stem down to foliage level encourages the development of two new flowering stems. These will be shorter than the original, but you'll get a longer blooming period.
Best wishes with your snaps!
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