Now upsell them on a water filtration system for their irrigation system.
If rust is that bad I'm hoping they have one for the household water!
Filteration systems do not work for irrigation systems after the fact , they restrict the flow and reduce the pressure , which in turn reduces the coverage on the heads and creates brown spots . Creating a larger problem Most people dont want the irrigation run thru their water conditioner on the initial install, due to about a 200% increase in the conditioner chemicals and a 50 % increase cost of the irrigation installation due to an increase in the number of zones from lack of flow and pressure , you have to run less heads per zone. There is an injection system available , but customers hesitate, it requires an upgrade to the backflow preventer to an RPZ , and a chemical holding tank inside , total cost of the system installed is $ 3200.00 adverage plus chemicals .
Looking at those pictures , some adjustments are necessary and possibly a wind switch , made by hunter to disable the system on windy days to stop wind drift should solve the problem . Or leave it alone and clean the fence again next year
Its a great upsell , if you know what you are getting yourself into .