Of courseEverything there looks appropriate, other than the fact that with Peat and Perlite, you want your pH to be closer to 6.0.
Since that doesn't look like your immediate problem, have you inspected the leaves of the affected area with a loupe or magnifying glass for pests?
When you get a single branch going funky, it could indicate pests. Looking at the pictures provided, I can't see any signs of any specific issue. Can you take closer up pics of the affected area for more detailed inspection?
I will inspect the presence of pests that might be the problem