Acers lots of dead wood this year.
My two acers are 19 tears old. Always been in pots and potted up as advised by grower. Last couple of years they haven't looked their best. This year potted up. Local garden centre says they are probably shocked but they've never looked this bad before. They have lots of dead wood in them. They already look like the leaves are shedding. One has flowered. The branch the seeds had formed on has already fallen off the tree.
When did you re-pot them? What compost did you use? Where do you keep them?
I have them in pots too and kept mine in the polytunnel this winter except for the two biggest. I brought them all out after Easter and gathered them on my north facing terrace, as usual. All was well with all of them but a combination of storm Miguel and the two heatwaves in June and July has left the two big ones with some scorched foliage and bare ends of stems despite being regularly watered and fed too.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
Amorphophallus titanum, also known as the titan arum took 8 years before it flowered.
You have probably seen the flowers of Sycamore ......Acer pseudoplatanus.
It was perfectly normal for them to have a few to many dead twigs.
These are normally noticeable in winter when bare of leaves.
I found it very therapeutic to just snap these off.
Your Acer has maybe been under stress with the recent very hot weather.
Wait till winter then just remove all the dead twigs or snip dead bits away
If dead branches are thicker use very sharp secateurs .
Never let the pots dry out completely,.
Move to partial shade if in full sun.
Give them some TLC.
It should be fine next spring.
This is flowers from Acer diabolicum
I would have potter them in John innes no 3 mixed with ericaceous compost.