I got cocky with my last batch and did the same thing. I ended up giving my surviving male away I was so disgusted not having a female survive. I will probably try a again with a compartmentalized tank setup next summer.
Good luck with that... in the meantime, check out this group on Facebook on ExCichlasoma Istlanum... Joining up there you'll learn more about this species.
Update on my Big Istlanum pair.... The males grown another half inch or so and the female seems to be coming into spawning mood again... Hopefully will have a supper spawning