Sago Palm Yellowing

Q. We have multiple sago palms in our yard and they have all done well for over 10 years. This year all the sago palms are turning yellow (pics below). Especially the largest one.

We have not changed any of the fertilizer or care routine and the watering is the same as the previous summers. For some reason this year they seem to be really suffering. Reading online some websites say too much water, others say not enough, some say too much sun, others say not enough fertilizer or too much!  Basically I have no idea where to begin... 😐⁉️We love our sago palms and love the dark green evergreen foliage (they normally have) please help us save these beautiful plants. 

A. It is  hard to begin. If they are healthy and growing in good soil they can handle a lot of sun and adversity. If the soil has been depleted (surrounded by rock mulch for instance) they can get quite yellow. 

If the roots are drowning and the soil stays wet they can yellow. If they have root diseases (too much water, poor soils or depleted soil) they can yellow. I would nurse them along until October and dig them up, amend the soil, inspect the roots and check for rotting roots, correct the soil/watering problem and replant them. The yellowing created by a lack of fertilizer or the right kind of fertilizer is different from this kind of yellowing. This appears to be stress related.

I think it is soil depletion which can be corrected by adding organics back to the soil. Use about a one inch layer of compost applied to the soil around them and water it in. You might also try adding wood chips, not bark, to the soil surface after the compost application.