Would a professor write a bad letter of recommendation?
I would read these responses as: "I am happy to write you a letter of recommendation, I am busy, and just want know where to send my letter".

As a professor, I get literally hundreds of emails everyday, many of which, like yours, I want to reply to, but I don't have time to write elaborate or detailed responses. I read the responses you got as terse but professional.

If I am approached by a student I don't feel I can write a good recommendation letter for, I usually tell them this, and suggest they ask someone else. I think this is common practice.