Hi it depends on catch location if they are wild or where their relatives came from if farm bred. It also goes on stress bar counts which I cant see here so you might have to work that bit out - found an article on cichlidforums that is really good for this
http/www.cichlid-forum.com/articles/is_that_a_festivum.php
I have broken it down here to the important bit.
M. insignis - Rio Negro and Rio Orinoco. 7 faint vertical bars. 2 and 4 are joined and the scales above the diagonal "flag" bar are reticulated.
M. egregius - Rio Meta, Colombia. Bar 3 divided into two.
M mirificus - near Iquitos, or Pebas. Divided bar 3 and there are think horizontal lines above the diagonal flag bar.
M. festivus- Southern Peru, Bolivia and in Paraguay. Bars 5 and 6 are joined.
M. acora- Rio Xingu and Tocantins. Divided bar 4
M. guyanae- Essequibo River in Guyana.
I think you have M.Insignis because they have the reticulated scales at the top - see how the light reflects differently to on the side. But this might be the photo. They should occasionally show their stripes and that is the best way of working it out.
BTW I LOVE the combo of Diamond Tetras and the Festivums
absolutely gorgeous combination!! Do you have a thread about your stocking plans or other fish you have with them - really interesting tank here
Wills