Containers – Causing Drainage Discoloration?

Q: I live in a courtyard home and use resin containers for all my plants. I have noticed that some of my older containers now produce a yellowish-brown water when I water them deeply. Are the containers are breaking down inside and producing the discoloration?

A: I think something is breaking down, but not the containers. As plant roots and potting soil decompose over the years, I could easily imagine drain water would be yellow or brown. This is much the same as the brown water of the Okefenokee swamp, resulting from tannins produced by rotting organic matter. I’d replace the potting soil if the plants seem to be declining.