Even if they didn't look like THAT, I'd say replace them. I don't like getting used batteries in ANY mod, because I have no way of establishing their genuineness and etc.
For more on battery care, safety, and authentic sellers, a little light reading:
https://www.e-cigarette-forum.com/blogs/mooch.256958/
https://www.e-cigarette-forum.com/blog-entry/baditudes-blogs.7609/
I believe your question may also be: is there something in the mod causing this to happen? I suppose it's a real possibility, but it could be your seller just handled his batteries poorly, not the mod itself.
If it were me, I'd proceed cautiously, give the thing a good clean, and keep a very sharp eye on your NEW batteries for wear and tear. It is possible the damage was caused by a drop or the charger or
something else, but I would just be cautious regarding the entire thing, and I would USE with caution. You may be okay, but if it's the equipment itself that is eating batteries, I would probably discontinue use of the mod.
Best of luck,
Anna