we planted them a month ago. they emerged from the soil two weeks later. looked perfect the entire time until this afternoon when I got home from work. several leaves are like this on two of our five plants. brown and crispy edges. coincidently, I watered them for the first time yesterday evening before bed. too much water? not enough? or something else?

If that is just the bottom leaf - then don't worry about it. They will lose those bottom leaves pretty quickly. You will have additional bottom leaves go yellow as the plant gets taller, just snip them off.

If the whole plant is going yellow, then thats another story. It could be to much water if you have been having the rain we have had, but not from a single watering. Dahlias love water once the have established their roots. I hear some aficionados water lightly, twice a day.

yeah, its the lowest leaf on that side. just bothered me because it was flawless until I gave it its first does of water, other than rain water. then BAM! crispy, brown leaves...