I cannot tell exactly what I'm seeing in the photo.... Is there a web on everything with flecks of light-colored things stuck in it? if so, it's probably spider mite webs that have what looks like bits of white flies (or could be aphid bits) stuck in it. Remedy is to spray w/ insecticidal soap. If it's not a web, then is it a fungus? little tiny mushroom like things growing from the stem? if so, I'd clean it off and assume they were encouraged to be there based on some decaying matter that they liked and an excess of moisture. I'd make sure it's cleaned and allowed to dry properly.

Your rail planting is GORGEOUS!!! (or will be again :)

I’m attaching additional close ups I just took

I'm not seeing any additional photos. I'd at least start by cleaning up the dead/loose debris.