What has happened to my dahlias?

Can anyone tell me what has happened to my dahlias? The 3rd picture shows healthy plants that I had potted up after overwintering the tubers. I had never done this before and was quite pleased with myself when they all began to shoot! I waited till nearly the end of May before planting them out and there has been no frost since. Imagine my dismay when one morning I noticed that the plants were slowly dying off from the top down. I am really hoping someone can help me save them. Thanks in advance.

 

I don't over winter Dahlia tubers, just leave them in the ground , so probably not much help. All I can say is that the ground looks incredibly dry, so that might be a good starting point.

To me they look very tall and leggy to which will weaken the main stem . In the early growth stages I pinch out the growing point to encourage them to bush out with new shoots, I also keep them compact too . Once they get into full blooming mode I leave ( apart from regular deadheading ) to do their own thing.

Here are a couple of mine that I've just taken a pic of.

 

Sorry how rude of me ,I meant to say hello @Schofe56 and.....

 

Did you harden them off, it looks like they have just not liked suddenly being put out in full sun drying winds etc.

 

Thanks for your replies. Pete, I hardened them off by putting them out at night and bringing them into a cool lobby at night for about a month! Upsydaisy, I have dahlia envy! I did pinch out the growing tips but followed advice I’d read online and didn’t do so until they had set 4 sets of leaves! JWK, I have been watering them religiously but, oddly, they seemed to start dying after we’d had a lot of rain!
Any more advice gratefully received.