|You are correct to focus on skills and qualifications during the interview process. As you noted, employees are protected from discrimination based on having a disability. This also includes having a record of a disability or simply being perceived as disabled.
It’s important not to make assumptions about a candidate’s ability to perform their job based on their having disclosed that they have a disability or other health condition. An employer can ask all candidates if they are able to perform the job either with or without accommodation; as a best practice, however, we recommend asking this on the written application rather than during the interview. If a candidate at the post-offer stage requests an accommodation to perform the essential functions of their job, then you would engage them in the interactive process to determine whether you could provide an accommodation.
In the future, you should counsel employees who conduct interviews not to solicit or document information that a candidate discloses regarding their inclusions in any protected class (e.g. disability, sexual orientation, national origin). This will help you avoid the appearance that such information was a factor in the employment decision.
For the current situation, I would recommend just continuing to focus on the skills and qualifications of the candidates that you have. If you do choose another candidate, you should able to justify the decision based on those comparative skills and qualifications and be able to show that the chosen candidate was truly a better fit.