We have a water softener and iron filter for the house. This is the drain line from the R/O that connects to the sink drain lines and likely got something washed into the port or line recently. Thankfully it was an easy fix.
A spin down filter is easy to install for your house and an irrigation valve can be fitted to the drain port to automatically flush the filter on a schedule.
That sounds like what I need to do, I just need to put it on the list of things to do as well Lol!😇👍☺️