https://taxpayeradvocate.irs.gov/get-help/audits-by-mail Is a great place to get help. This is the taxpayer advocate address.
No need to worry. This may just be routine. Just respond to their question and give them what they request. Do not give them anything more or less.
**I don't work for TT. Just trying to help. All the best.
***Say "Thanks" by marking as BEST ANSWER and clicking the thumb icon in a post and that I solved your question
**Mark the post that answers your question by clicking on "Mark as Best Answer" I am NOT an expert and you should confirm with a tax expert.