I think you are good to go They should lay again. Probably on the slate
When they laid last time was it in a community tank?
If it was it is possible the other fish may have eaten the eggs too.
Are you going to try to let the parents tend the eggs the next time they lay or are you going to remove the eggs?
Did you check out the link I posted?
If not check it out lots of usful tips there
here's one more link
http://www.geocities.com/river_angels/breeding1.html