Calcium and Snails/Plants

I have a 65g tank ... with a snail problem, meaning that I can't seem to keep Malaysian Trumpet snails going for very long. Their shells slowly turn white and disintigrate. What's puzzling is that the pond snail shells seem to be ok. I do have some assorted EI/Co2 issues with the plants, but I am working on those. What I want to figure out is what is bothering the snails, which no doubt affects the plants as well.

My tap water has 0 kh so I add baking soda and bring it up to 8. My ph is 7.0, meaning I have co2 of 25. I use the EI and change 50% water weekly. I add the following to my tank:

Prime
Baking soda
Potassium nitrate to 10ppm
Potassium phosphate
Flourish potassium (a little extra which keeps my crypts from getting holes)
Flourish fertilizer

0 ammonia
0 nitrate
0 copper
25ppm co2
kh 8
ph 7.0

I want to make sure I have good snail life before adding shrimps.
Is calcium the problem here? If so, how do I add it and how much for a 65g? Does it affect ph/kh? I thought if my kh was 8 I had no problems. If there's something I need to add, I shop on Greg Watson's website, so telling me what to get would be appreciated. Thanks!

 

Re: Calcium and Snails/Plants

Thanks, I'll test the gh and order the booster from Greg Watson. I appreciate your answer!

 

Re: Calcium and Snails/Plants

Just tested my gh...it's 0.