Frogs should be kept in their own tanks because if the fish get sick, any medication used to treat them will usually kill the frogs. Frogs will also eat small fish, shrimp and snails.
You need to get rid of the assassin snail or it will kill the nerites and mystery snail.
I would move the assassin snail and frogs out. Then add a few more neons and black neons so there are 10 of each species, then leave it at that. The platies will breed and before long your tank will be overcrowded.
If you have 3 filters on the tank, there might be too much water movement for the fish. Neons and black neons come from relatively calm water and don't like of need lots of water movement.
Can you post a 1 minute video of the fish tank so we can see how much water movement is in it?
You can upload videos to YouTube, then copy & paste the link here.