How much water are they getting? They grow in ephemeral bogs in their native Africa.

A couple of times a week. I'm guessing the soil needs to be kept damp at all times?

That was going to be my point Tugb. This Arum looks to be close to a wall so won't necessarily get a lot or rain... soil certainly looks dry. Water on a regular basis Justine and not just a quick sprinkle with a watering can, put the hose on trickle and let it stay like that for an hour or more.

Thanks guys for your help.

Be aware this is going to be regular problem for you as Arums need a lot of water. They happily sit on the banks, or in, burns and other water courses. If the area you have planted them in is constantly dry you might need to think again.

is it in a pot its had to tell if yes you could put the pot into an ornamental bowl/bucket dish to act as a reservoir.
I have mine sitting at the edge of the pond.