Mystery Snail Shell Okay?

[KribensisLover1]

Hello! I got a blue mystery snail a few days ago and the shell at the front seems more fragile and lighter colored than the back. I thought it was fine as the snail is super active but I got another ivory mystery snail today (much larger which wasn’t my choice) and the ivory’s shell looks healthier. Is the blue shell okay? I love her and hope so! Also is it okay that the ivory is so much larger?

 

[BettaDollar]

Nice snails.
IMO - I wouldn't consider either thing a problem. Different sizes shouldn't be an issue and new shell growth that's lacking color & looks thin or fragile can color eventually & harden more too.
Hope you don't have any puffer fish! That could be a big problem.
You could consider crushing eggshell to a powder and sprinkling it in your tank a little once a month. It shouldn't affect your tank in as small a quantity as you'll use.
Some people use a piece of cuttlebone in place of eggshell for the calcium snails need.
It's used for parakeets - to sharpen their beaks.