Evergreens with yellowing leaves

Strange if the soil is acid - that's what Skimmias like. Viburnums on the whole don't mind - except for V. lantanoides which needs lime-free soil. It really does sound like chlorosis - maybe the rain has leached away the nutrients? Try a dose of Sequestrene on the Skimmia which might perk it up. Mulch round both with home-made compost and give them a feed of blood, fish and bone in the spring. I hope it works.

Many thanks Spitzhenry. I thought that was probably the way forwards but just needed some reassurance.