also thats the female on the left in the top picture. notice the dorsal (top) fin is shorter on her than the male? its subtle but pretty good way to sex without venting them
i have a friend who has bred severums recently in new zealand if i remember rightly he romved the stone with the eggs on and then put a small internal filter against the eggs to improve water flow oer the eggs and he's hatched his.
Next time they spawn, I would try removing the eggs. I had a pair of green sevrums that ate em every time they were left in the tank. Its still cooler to watch them raise their own fry, but sometimes, you get stuck with bad parents.