sick snail

Someone please tell me what’s wrong with my snail! I have two (turbo?) snails, one is acting completely fine! There’s plenty of algae in here for them too. This one was upside down in the sand last night, seeming to try and grab onto the rock. I moved him next to a rock so he could easily get...

I have been aggressively changing the water as well (about 20% weekly) to see if i can help them. Sadly they are just dropping like flies. All of my frogspawn and wavy corals have died as well. All of the regular tests look perfect but I think that there may be a heavy metal that i am missing...