First, go ahead and reply that you made a mistake and should not have filed the 8885. Make sure to ask them to tell you what they want you to do next.
The following is what is typical for a 12C, but let the agent tell you specifically what he/she wants. The following may be helpful for when the IRS agent responds.
The IRS says that in response to a 12C letter, you are not to file an amended return (please see https://www.irs.gov/individuals/understanding-your-letter-0012c).
Now, this does not mean that you should not amend your return in TurboTax - this may be the only way to get the forms corrected that you need to send to the IRS. Just don't mail form 1040X to the IRS.
In these situtations, the agent sending the letter will give you specific instructions on what they want and where to send it. Typically, if some amending is to be done to your return, the IRS agent will do it when he/she receives your changed forms - that's why they don't want the 1040X.
