I ended up moving the pair to my 79 g. There are a thousand places to hide and a very heavy plant mass to hide amongst as well.
I find the males of each pair keep nudging the female's belly and then turn around and wag their fin in their faces. Females are not interested at all and either go sideways when approach or swim away slowly.
Have you ever had a pair take a very long time to want to spawn? Or could it not be a match? Would adding another female cause stress to the other female? The females aren't stressed at all..the males aren't chasing them aggressively, just a nudge like "hey, whatcha up to? Wanna hook up?"