I've read that if it's fast moving, then it could be bacterial, and slower moving could mean fungal. I've only had one experience with something fast moving, and I'm no expert either.
I would treat it with a systemic fungicide, and cut off any possible infected areas. (This is was I did for possible bacterial infection, and it seems to have slowed things down at least.) you can wait for other suggestions, I'm new and definitely not the most experienced.
Have you checked the roots? The leaves look droopy in the first photo
if you've been watering normally, I think droopy leaves can signal a problem with the roots, such as an infection. (Sorry if I'm incorrect)
I got some generic cleary's
(systemic fungicide) from amazon that was relatively inexpensive.