Maybe it's your lighting, but to me the dorsal looks like it has a very dark area, which usually indicates female. To compare, some photos below of Herichthys carpintus chairel
female
male
many of the Herichthys complex look very silmilar, and it would be difficult for me to differentiate by that pic, below a pair of Herichthys tamasopoensus
another shot when the tamo, was younger