You have spider mites. Very common affliction for many indoor plants in winter due to very low humidity and warmth.

Spider Mite Control

all my houseplants are taken outside in early fall.. and treated with a systemic granular media based product.. and left to do that job outside ... and a few weeks later.. they are all brought back in the house.. and remain bug free for the rest of winter ...

if you decide to use such ... make sure the label notes it can be used on mites ... as some insecticides may not work on mites .. some do.. some dont ... they arent insects ...

an ounce of prevention is worth a pound of cure..

isolate this plant from all other plants ... asap

and btw... those leaves wont look pretty again ... so you will have to watch new growth.. to tell if you have an ongoing issue .. when it stays clean.. the plant is clean ....

ken

btw.. great pix ....

The link helped a lot @gardengal48 (PNW Z8/9)

Thanks Ken. I often do that. It is probable that this year I was a bit lax.... :)