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If they are hybrids I would refrain from breeding them at all.
I can't tell you a number. It's just that I personally have no idea which other nijsseni-group species it could be and together with the deformed scales of the male, for me, hybridisation is a likely explanation.
Maybe A. (cf.) sp. Nadelstreifen. They are found near Leticia where also a form of A. cf. bitaeniata is found. But without knowing the catch location or seeing better pictures of the fish in different moods, this is merely one of several possibilities.
"don't always" is quite euphemistic ;-) Show some pictures of them, preferably in different moods, then it should be possible to tell whether they are in fact D39.
Btw. the correct name is A. sp. D39.
Watch out for the metallic green/blue lip spot shown only by males of all agassizii-sublineage species. It is found on the lower part of the upper lip near the corner of the mouth:
The larger fish (male) shows a caudal pattern not typical of A. uaupesi. It could be A. lineata, but from this photo alone and without knowing the catch location, it's impossible to tell for sure. The smaller fish is for sure not uaupesi because it's a macmasteri-group species.
I see nothing that speaks against viejita - it might just be a particularly colorful specimen.
However, I have seen similar fish showing more red coloration on the head than typical viejita that were said to be from Cumaribo (Vichada). So, I would better call these A. cf. viejita and never keep...
Mostly gut feeling supported by the shape of the head and body and the narrow lateral band. If your fish show abdominal markings or horizontal caudal pattern or a downwards widened suborbital stripe as in the following picture, you can be 100% sure: