I am amending 2017 taxes from married joint to married file separately. Completed the amendment for my spouse on the 2017 taxes. How do I amend the for me?

[Opus 17]

It is not allowed to amend joint to separate after the deadline (April 15, 2018).

Potentially, if you allege your spouse filed a fraudulent joint return without your permission, the IRS might look it, but that’s a nasty situation and may require the assistance of an enrolled agent.  

For a regular voluntary change for strategic reasons, you are too late.  

[SweetieJean]

Opus 17 means April 15, 2018 (not 2028).