This house had all the gutters draining into 1 downspout.

There are quite a few in this area like this.

I noted the sheathing issue.

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i believe the rule of thumb is something like 1 downspout per 25 ft of gutter.
The 2nd story gutters look fine, until you consider where they discharge.

:—) How many layers of shingles are there? (pic 3) Looks a tad bit thick. Honest only one.