Empty White Ramshorn Shells

[AdamScott]

Hi all. Recently I've noticed my blue ramshorn snails have been dying off over the last week or so - all that's left is empty white shells as shown in the pictures below. I also have a few nerites, pond snails and MTS snails in the tank as well that seem to be doing fine. I feed 2 algae wafers every 3 days because i'm already dealing with slight overpopulation with the pond snails. No fish or other species besides those snails in the tank. Tank has been established for roughly 4 months and has grown quite a bit of algae on the glass and on the plants. Any idea what could be causing this? Water parameters below:

PH: 7.5

Ammonia: 0

Nitrite: 0.25

Nitrate: 0

Hardness: 100ppm

KH: 80ppm

Water temp: 81 (maybe a little too high?)

[Colu]

It could be a mineral deficiency I would start feed hikari shrimp cuisine it has add calcium you could add some wonder shell or mineral blocks 

[CalmedByFish]

Same problem here! My ramshorns are dying, while MTS and bladder snails are fine. Super frustrating. 

My ramshorns devoured every speck of algae on the glass and hard surfaces. Guessing they might need algae, I actually bought them Chlorella tablets, which they absolutely love... but they're still dying. I've added a piece of cuttlebone to the tank floor so they have access to Calcium, but they ignore it. 

I'm baffled, and will be following this thread, hoping for answers.

[CalmedByFish]

I should add that I also feed them Crab Cuisine (intended for animals with shells), and they eat fallen Xtreme Nano that the fish miss.