Cleaned / bleached all pots. Rinsed off outside to remove excess soil, then soaked in tub with bleach for a while, then rinsed off and air-dried. What a huge task.
Hopefully this will help prevent whatever last year's problem was where everything inside became terribly stunted.
(wrote this note on Feb 16th but it was a couple of months ago when I did this task, so guesstimated Dec 20th)