Interesting Rolla. My guess would be to move the new pair into a tank of there own and see what happens. The first pair you may want to sell. Knowing they are a pair would make them appealing to buyers. Or move them back into main tank and see if that younger pair can inspire them to follow through.
It’s new to me but I now have 3 pairs laying eggs in my tank. The first pair laid eggs and watched them for 3 days than they were gone. A second pair a few days later laid eggs no more than 5” from the first. As this was going on a third pair laid eggs on the opposite side of the tank right next to where rams were laying eggs. The second pair watched the eggs again for 3 days and the eggs never went white. But we’re gone on third day as were all the others. So my question to you is how long till they become wigglers? Than swimmers? Thanks.