To the best of my knowledge, most, if not all, aquatic snail eggs are laid in a jelly mass so I doubt those are snail eggs. The quantity of eggs makes me hesitant to say they are Angelfish. Most Angel spawns, even first time spawns, average 100 eggs. BA Tetras are egg scatterers as are most Rainbows but depending on the types of rainbows you have, these could be Rainbowfish eggs. (Celebes Rainbows are known to spawn on plant leaves and would not have a large number of eggs.)
You did not mention having any catfish or scavengers besides the snail but the quantity of eggs could be cory catfish.
Lastly, and it's a long shot
, are you sure the eggs didn't come with the plant?