Should I put the papers that I contributed only a little to on my CV
Your list of publications has to be complete. You should not omit any papers for which you are an author.

If you are uncomfortable with some items on your list, you may add a note on why you happen to be a co-author, but dropping some work is not a good practice. 

In your case, I'd say that there is nothing wrong with these publications: The other authors agreed that your contribution was worth co-authorship and that's usually ok (assuming that the other authors know their field and acted appropriately). If somebody asks about that paper, you can frankly say that you did the calculations but that you can not answer questions about background/other parts or such.