and what do I do? Tree still seems healthy and apples seem not affected.
mark in MN
Your two links won't work. You have a gap in the .jpg. Close the gap in the address bar to connect.
Is it Rust?
I think that's cedar apple rust.
Here is a link that might be useful: Mark's picture link
with a spray bottle put a tablespoon of baking soda then fill 3/4 with water... or get a gallon size sprayer and put 1/2 cup to a gallon. Shake to mix. Spray that on the leaves. the baking soda will kill the rust. Any place red or brown is dead, the rest of the leaf will live. Rain will wash the soda off, so be mindful of that and don't wait too long before reapplying.
Be reading up on pruning and looking your trees over now as a learning exercise. It takes a while to actually get your brain around it. Better to know what you are doing, rather then just being a guy with clippers.