Unfortunately, it is now too late to amend those returns since you used an impermissible accounting method by not taking depreciation deductions for two or more consecutive tax years.
As a result, you need to file Form 3115 and make a 481(a) adjustment.
See https://www.irs.gov/instructions/i3115#en_US_202212_publink100035791
You will most likely need to use a tax professional for this purpose.
