Sunflowers are about to die as they're only annuals, and lots of us leave the dead flowers in place so the birds can have the seeds in the winter.
Normal for the flowered stems of delphinium to be hollow like this, same happens on lupins - cut out the flowered stems at the base, where they arise.

I've found in the past that slugs get into the hollow stalks and kill the plant, so I would suggest a little slug protection for them.

thanks that's helpful. I just read they're poisonous, i didn't realise that - does that include the flowers, leaves and stalks?

re- sunflowers. they're only the little ones and the seeds are little too, not the proper sunflower seeds. I didn't realise they were only annuals, so i won't get it back next year when it dies will i? i really wanted big ones so i might plant some seeds next time. thanks for your help

Delphinium might well be poisonous, as are more than 50% of the plants in an average English garden - but as long as you're not planning on making a salad with your plant, it'll be fine -ingestion is what causes the problem

thanks, feel a bit better now knowing there are quite a few. but i did think you could eat a lot of the flowers in the garden - i'll have to check up on them before putting them in a salad!

just google 'edible flowers'

oo good idea, never thought that, thanks

(~)