[Mystery snail turning white]

I got a mystery snail a few weeks ago. It was a light blue color. Now it's shell is starting to turn white. It started by its head and is slowly moving down the shell in almost a perfect line. Ive read in a few places that this could be a calcium deficiency. I added some spinach on Saturday then my nitrites spiked so I removed it and did a water change. Then I bought some wonder shells thinking they would boost calcium but didn't realize it would raise my gh as well. My water is already at 150gh so I am apprehensive to add the wonder shells. Thoughts?

Current numbers

Nitrate: 10 ppm

Nitrite: 0 ppm

GH: 150 ppm

Kh: 120 ppm

pH: 6.8

CL: 0

 

 

 

 

 

 

 

[Exclamation point rasbora tail rotting off]

I just noticed one of my exclamation point rasboras tail looks like it is rotting off. 

Nitrate-25

Nitrite-0

Gh-150

Kh-120

Ph-7.2

Chlorine -0