Photos are P 1. Small dark spots (september 21) have become in january 2022, grey clusters or pustules if i can say. My enlarged photos from an other tree shows brown areas around grey clusters. Your photo 1014.jpg from to day send to compare, shows the black invading the whole branch. Explanation: Blackening = cambium dead, that the definition. Below the thin bark of young Acer cambium is dead pseudonomas bacteriosis blackening don’t began with pustules or clusters. The filaments of a fungus growing in the green cambium => blackening and kill it. We are in présence of an wood pathogen, one of a large list producing cancers and dead of branches. --It is not Eutypella disease because Eutypella develop inside the wood, in the phloeme, so no blackening can be observed. All fungi wood cankers have the same annal process . During autumn/winter, the grey clusters produce reproduction which is dissiminated by rain and wind. Reinfection may occur repeatedly. The inoculum you have on yours trees i very hight, you can’t prune. Your climat predisposes to the fungal canker attacks , they are known to affect plants already weakened or poor growing plants. Prophylaxis. Copper treatments are PREVENTIVE =>sprays inhibit the reproductive organs. But copper treatments ARE NOT CURATIVE. (some exceptions exists for open bacterial cankers disease but not for fungi disease, they are closed). Plant tissu don't assimilate copper, so the sprays you are doing are not able to rich the fungus filaments of the fungi canker/ or few, perhaps 3 to 5%. I express a wish. Take time to visit Choteau nursery in Belgium, he is a very good grower, one of the best. Phone and take a date with Choteau father, speak clearly with him, he could be of good advice. A journey through there will enchant you.