Sorry to hear about the fry Lonewolf. Don't worry though, they'll try again soon. Mine are spawning every week or two. They haven't actually raised any fry yet, but each time they last a bit longer. Hoping the next one or two attempts will show some results.
Maxwell, sexing gets a LOT easier one they're older. Half the time the ones in the store are very juvenile so they're harder to tell apart. A lot of times on the young ones you can tell the males because they don't have the pink belly, most of the time. What makes it real rough is when they're young the fin spikes are all tiny and either sex might or might not have a pink belly to start with. It's hit or miss, but the best odds I've seen are going by the belly color in comparison with the others in the tank.