Have you checked for spidermites at the stems? Mine tend to get that here. Could be leafhoppers too.
Do you get oleander aphids on your buddleias? My buddleias is surrounded by milkweed infected with oleander aphids and so far, they stay off other plants.
That is quite a while in the ground already so you would expect them to be drought tolerant already, right? The first thing I can suggest is to water a larger circle around the plants. The reason is I have transplanted a couple of buddleias over the years and they have can shallow roots that run along the ground beyond the drip line. Maybe yours is the same.
I have had mixed luck with buddleia. I've bought several over the years, but some never become much. They don't make the first winter or I have removed most of them due to small flowers and awkwardness. However, I have a couple, including Wysteria Lane, that do well. Wysteria Lane has been in a frost free pot above ground since I got it. That is one that I cut way back when any danger of frost is over to get the weeping form but notice it isn't a favorite for pollinators. How about you? Right now, I bought one that is droopy every afternoon so far - Grand Cascade. Yet Blue Pugster does not droop. It is also came in a larger pot.
