Rust around rear screen drain holes on 911L

[gdupl0ck]

As you can see from the attached image I have rust problems this is on each side where this drain leaves the side pillar into the pipes. There is also slight bubbling on the outside as well.

I am thinking about getting Rear Window Corner Repair Panels from Design911 to get this repaired. I don't think this panel includes the drain exit though.

Any thoughts on this?

Why are there drains as there does not seem to be anywhere water can get into here accept from the rear screen seal?

Thanks