Here is a photo of some skimmia that are struggling. There are others nearby...
Here is a photo of some skimmia that are struggling. There are others nearby that look OK, so far. Two of them have recently been replaced. There is an irrigation system running on either side of the plantings. Too much water causing the chlorosis?
Skimmia is an ericaceous plant requiring acidic soil, so you may want to have the soil tested to ensure a pH of about 4.5. They also have shallow roots that do not like to be in consistently moist soil. So, given the weather we have experienced and your mention of an irrigation system placed around them, chances are: excessive soil moisture is the culprit. Back off on the watering and provide them with a little iron sulfate.