Help with Buddleia/Butterfly Bush

Help with Buddleia/Butterfly Bush

One of my butterfly bush plants (Buddleia davidii - Honeycomb) is doing poorly. It has an increasing amount of yellowing leaves, both on mature and new leaves, and the branches are getting woodier. I'm finding more dead wood than live. I haven't noticed any bugs on the leaves that might be causing damage. I pruned it last month and reduced its height by half, hoping to encourage new growth. But it seems to be getting worse. Should I attempt to prune it again? I've never pruned this late (I'm in zone 7/8 in TX), so I don't know if it would be okay. If I should prune, how much should I attempt? Could this be the cause of yellow leaves? Photobucket I know, it's far too spindly. PhotobucketAll the yellowing and dying leaves look like this. Thanks so much for any help.
FINALLY!

FINALLY!

Seeds

Seeds

Selection of garden photos from this week

Selection of garden photos from this week

My New Apartment!

My New Apartment!

Coming By Mail

Coming By Mail

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Doo Doo Doo, Lookin’ Out My Back Door…