Posted: 06/12/2015 at 12:43
Hi Stuart - I don't think there's too much wrong with those. The middle one has flowered, and that has taken a little bit of effort on the part of the plant, which in turn has caused a little bit of yellowing, because it's used up it's resources. Nothing much to worry about, and all evergreens will drop leaves and have yellow ones at various times.
Cutting back a little, will restore the balance to the whole row, and give them all a chance to grow on more evenly, growing outwards as well as up. It's for aesthetic reasons more than anything that you'd do all of them equally, so just take them all back to the height of the smallest one, having cut that one back to new set of leaf joints, as nutcutlet said, to tidy it up