Exterior overflow PVC pipes discoloring

The additional condensation is probably from a coil that is cooling more and removing more humidity fromt he air.

The stains are caused by gunk that the water is picking up in the drain pan and the coils. Have you ever cleaned them?

Even clean water dripping on the siding will collect dusst and dirt. The cure is to fix it so it doesn't hit the wall. Of course cleaning the pan is a needed maintenance item anyhow.

Harry K

No I have never cleaned them or the drain pan. The drain pan would be found in the ceiling unit right? Not the outside unit? Thank you.

Correct, it is where the moisture from the coils drip into. . Flush it with water and some sort of non-sudsing cleaner. Some bleach won't hurt. You may want to try putting something down the tubing, like a thin brush on a long wire to ream it out.

Condensate pans are not often seen and thus not thought about until there is a problem. Give it a flush every spring and again after the AC season.