Thanks for the info. I will try the hydrogen peroxide the next spawn I get. It is too late for yesterday's spawn as I already used Methylene blue. I will begin to change water in the hatching jar to begin getting rid of tge methylene blue. What strength hydrogen peroxide did you use? Ammonia from the air could be another possibility I never thought about. One of the 20 gallon tanks had a sponge filter but the second one had only an airstone. My setup looks very much like your setup. My suspicion is genetics. Both spawning pairs are brother and sister. I may need to acquire a couple more fish and see if I can get another pair as I have five fish that have not yet paired off.

I use 3% peroxide at 1 ml per gallon of water.
As for the ammonia, it was the last thing I ever thought would be the issue but I tested the air and found it there. I even set up an air pump outside so it was pulling good air and the bubbles in the tank would add it through the exchange of gases. It was the ****edest thing.