Apple Snail shell color

[Fishy Momma]

Hello, I have a new Apple Snail named Rocky (for obvious reasons) and his shell is changing color. He was completely light gray when he joined the tank on January 29. Now, about the first 1/3 (front) of the shell has turned a darker gray. This is what I call the "new growth" area, although the size of this area hasn't changed since we've had him. The shell looks healthy, just darker, so now he's two-toned.
He is very active and seems to be eating. His diet currently is shrimp pellets, flake fish food and algae wafers. I tried a carrot, but he didn't pay much attention, so I removed it from the tank. Havwn't tried any greens or cucumber yet.
About his environment, a Fluval Edge, 6 gal tank. Tank mates are 2 fancy male guppies, a Cory Catfish and 3 Neon Tetras.
The tank had just been cleaned the day he joined us. Checked the water pera meters last night and both the PH and alkalone levels read normal.
Any ideas or words of wisdom...anyone? Thx.

 

[Solitare142]

My unsexed Ivory is doing the same thing. The only difference is that the 'new' shell is much much healthier, so maybe that's it? I got him/her this past week to help Betty, my black mystery who's been lethargic since my golden, Harold, passed.

 

[Fishy Momma]

Hi!! I've only had Rocky for about a month, but we're starting to think maybe this darker shell is "new" shell growth. He is a bit bigger than when we got him, but there is about 1/2" oF darker shell and it would seem to be a lot of growth in only a month. It is very healthy looking vs the original shell's lighter color. He came along following our golden mystery Sheldon, who was with us for about 3 years and topped out at about 1 1/2" diameter. He's still with us, as we kept his shell since he was so handsome