Since you are just discovering the suspicious information, I would use the 12/2018 to 7/2019 dates because it only becomes suspicious when you determine you have enough information to make that call. I have had this in the past and it is not considered a late filing because you put in the date of determination which would be 7/30/2019.
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Define Success on your own terms, achieve it by your own rules, and build a life you are proud of. Anne Sweeney