The face board was all sorts of crooked and cattywampus. The corners didn't meet up right. When we bought the house the gutters were slam full of leaves and dirt, so they probably never got emptied, and the water overflowed and got behind the tin. There was a tiny bit of rot on the face boards. The roof plywood was good/solid/dry so I think it's from overflowing gutters.
I couldn't get the corners/sides to straighten out so I replaced both sides and the front corners. I also added a 2x6 brace to pretty much every joist.
Also not shown in the pics is the 4' gap without support on the left front corner (both sides). I added a 2x4 to span the gaps. I obviously couldn't tie the plywood roof to it, but it's nailed to the face board and porch joist, so it's at least holding up the plywood now.
Edit, added pic of where I added support. Imagine the roof with just the corner truss then a 4' gap on each side
The other side was done correctly. Must have ran out of 2x4's that day...