Hi Warren, It's hard to tell from your photo what exactly is wrong with your snapdragon. They thrive in the cooler temperatures of spring and fall. I wonder if the weather was too hot, they didn't have enough root system to keep them hydrated, then the soil was waterlogged (the root system was small so not able to utilize the water). Too much water causes the plants to exhibit the same symptoms as too little water.

I wonder if you might just be happier to start over with new plants. (The picture makes the plant look dead. Perhaps it isn't as bad as it appears.) Your other option is to wait to see if it revives with the reduced watering schedule.

Hope your plants revive and thrive until fall freezes come.