they are probably mating. i've seen my snails do that but never seen them lay eggs....
maybe try and feed them more. that encourages breeding, try and feed them foods such as
certain fresh vegetables
These guys I think will lay their eggs above the water line in clusters, make sure you have at least a couple of inches of air space above the tank and that your lid fits firmly, so that there is an area of high humidity above the water level of the tank