If they're in containers it could be vine weevils. Their larvae eat the roots, and that would cause the plant to shrivel up.

If you tiped the plants out, you'd be able to see the white grub-like larvae. You'll have to kill them all, or dispose of the compost.

You might be lucky if you replant the Acer and Fuchsia in fresh compost, that they might re-root, but they might not.

You can buy stuff to kill the larvae. It's called Provado I think. You mix it in water and pour it on to the pots. It is taken up by the roots, and then when the grubs try to eat them, they get poisoned and die.

I am not saying this is what it definitely is, but it just could be.

That looks like a water problem to me - that is, not enough of it. Acers can frazzle in the sun or in the wind, so it might be that as well, so if that's in a very sunny spot at midday, or is in a windy position, try to move it somewhere more suitable. As for the fuchsia, I can't tell if there's any of the plant left alive, the bit you show in the picture looks completely dead. If there is some alive, cut it back to that and increase watering.

I agree with Bamboo re the sun or wind. Neither like to be baked on a patio with hot walls & paving stones around. Put them in the shade, hopefully they'll recover.