Disease killing two acers - stumped.

Hi, I have two acers in London that are being ravaged by a fungus or something. I've googled it and couldn't find anything.

The first one to succumb was Acer palmatum'Deshōjō' (red leaves in the foreground in the below two photos) and I cut out the main trunk with the fungus. The few branches left at ground level seem to be ok now.

https://preview.redd.it/dain65o2cu7h1.jpg?width=4284&format=pjpg&auto=webp&s=98f5ebc20ed575b32e8de269c0f4beee21a109c3

The second acer, Acer Palmatum Katsura in four photos below, got the same on its main branch. I cut out the worst of it but didn't want to cut out the heart of the plant. It seems to be growing well now but the fungus is still on the main trunk and I don't want it to spread. Any advice is much appreciated!

https://preview.redd.it/r7ksy4o2cu7h1.jpg?width=4284&format=pjpg&auto=webp&s=657a1c7d3abbb274ecba1c210367847cb1e729fa

https://preview.redd.it/oexjv4o2cu7h1.jpg?width=4284&format=pjpg&auto=webp&s=ebb9996d7c1b2152fb128440c00dff565357e70c

https://preview.redd.it/nqyd36o2cu7h1.jpg?width=4284&format=pjpg&auto=webp&s=6bad055b1337257a11aaaae84b60144016c8f123

https://preview.redd.it/au23e5o2cu7h1.jpg?width=3024&format=pjpg&auto=webp&s=2dac3ff6fa3d67b8814d44797622264dee05ad4a