You are 100% on those lightning cables. I've gone through countless ones.
Strange. I am still using the first lightning cable I got with my iPhone 5. Have since gotten a 5s and a 6 and just left their cables in the box as spares. My daughter has an iPad Mini that is still on its first cable and it is 2.5 years old. My wife has an iPhone 6 and an iPad Mini that are both nearly a year old and still on their original cables. What do folks do with their cables that causes this corrosion? I can't imagine.