To answer on of your questions, Cons will breed no matter what, simply because they are cons, they do it all the time whether you like it or not.
What is your male/female ratio, temperature, tank size, any tankmates, etc? Are you conditions right? Yellow labs are fairly easy to breed, I had them in a 60 gallon way back then, and they always bred for me, I had the temp at 78 and the ph was around 8. I had 2 males and 8 females breeding a lot.