My Hostas are very poorly

In my experience, this is how Hostas look when they react to Autumn on the way. It's been a funny year for weather so maybe, after all your rain and low temperatures, the Hostas have decided it's time to snuggle down? You could dig them up in a week or two, split them and replant in smaller sections apart from each other, just in case there is some disease. They'll die down and come up again next Spring.

Thank you Nariz. I forgot to mention that I only bought them a couple of weeks ago, they've been in the ground for about a fortnight.

For newly planted they look short of nutrients and water as the soil looks really dry to me. I think I would leave the hose on here gently one evening for a good hour or so and mulch with a thick layer of compost after. Also if the sun is really strong shade them with an umbrella this year.

I agree that a couple of them are looking a bit Autumnal, a couple of my lighter ones are looking similar. So could be the weather.
I can't offer much more than Drc's advice - that soil is looking rather dry and they will benefit from a good soak and mulch. It maybe too late to get them looking any better this year but if you follow this advice it can only benefit the plant to make it stronger for next year.

I would only add that they may be planted a little too close together as well.

Thanks everyone.
I wondered if I had put them rather too close, but thought I could take one out in a year or so if they grow too big--don't know much about hostas!
Now I'm off with the hose pipe and compost.........