Inherited IRA RMD not taken

My wife received an inherited IRA from her deceased mother at the end of 2014. Since she was under 70.5 we thought no RMD was required. We just found out we needed to withdraw about $500 for each of 2016 2017 and 2018 tax years and need to file amended returns for each of these years along with forms 5329 for each year. We plan to file a waiver request with the 5329s to try to eliminate the 50% penalties.  We never got 1099Rs for these years from the banks holding the inherited IRA. Can you provide any assistance in filing the amended returns and 5329s?