Here's something that worked to get mine to breed:
Over 3 weeks creep the temp up to 30degrees C and feed a lot.
Then, when you do a 40% WC reduce the temp to 28degrees C.
The temp drop thing I stumbled on when I accidently left the heater unplugged and my pair spawned that weekend! Lucky for me it was the end of spring and high 20's though!
Hope this helps with your fish.
J