What were they in before you planted them? If in pots with good root system established then you need to check the ground where you have planted them for water logging. Sometimes if you have a clay type soil you can plant something into a soil bowl that will hold water. This means the roots are sitting in water and that is not good. If that is not the problem it could be the bad weather we have been experiencing and they have picked up one of the myriad of sickness going with it. I've had them look pretty much the same as you describe but if left they may start to shoot again from the base. I don't know if they sulk when being moved like some plants. I'd leave them for now and see what happens but do check the roots water water damage and pests.

Sun is important - in full sun they have a better colour, but they do tend to darken down as they age.