What is the GH and KH of the aquarium water?
If it's 5 GH and 10-11 KH, and the GH and KH of the well water is 0, then something in the tank is raising the GH and KH.
Guppies like harder water with a GH around 200ppm and are fine with the pH between 7.0 and 8.5.
You could add a Rift Lake water conditioner at about 1/3 to 1/4 strength to increase the GH and KH more, but it might push the pH a few points higher (8.0-8.5).
--------------------
If the snails have suddenly stopped moving about then there is something wrong with the water and a big (75%) water change and gravel cleaning the substrate should help. Cleaning the filter should also help.
--------------------
If the plants are struggling, then something isn't right. Post a picture showing the entire tank and tell us about the light, fertilizer and CO2 regime you run.
The GH is 5 The KH 10 The tap is 0.
There is a piece of lava rock, petrified wood, drift wood, and a small rock that I was told from the fish store was lava rock but now I'm not sure. It's been in the tank for a year...as long as the other rocks and wood. The substrate is black fluorite. (I am attaching a picture of this small rock).
I was running CO2 for 8 hrs a day starting 2 hours prior to light. The light is the stock light that comes with the Fluval Flex 9g (7500k and RGB LEDs). I haven't run the CO2 in almost 2 weeks.
I was using Seachem Flourish fertilizer and root tabs for the past year. On March 25th I switched to the Aquarium Co-op brand fertilizer and root tabs to see if I would get better results. No difference except the root tabs are really capsules that release into the water if the substrate is disturbed. I contacted the manufacturer and was told the contents are perfectly safe for all of my tank inhabitants if it gets into the water. I also switched to Seachem Purigen instead of the activated carbon at that time.
I've been doing 50% water changes every few days for the last several months because I ended up with more guppies than intended and I don't want an ammonia spike. I rinse the filter sponge in tank water, vacuum lightly, and add Seachem Stability with every water change. I clean the pump and the glass about once a month. I was adding Prime initially to prevent ammonia spikes, but haven't in a few weeks. I don't have chlorine in my water. I also added Flourish Advance a couple times at the beginning of this month but that was all.
On May 7th I noticed one of the snails was moving slowly. It looked like there was blood lining the inside of the shell. I don't know what would have caused it. The other snail was fine. The ghost shrimp shell started to look a little crusty. I tested my calcium with a Fluval test kit and it showed no calcium. The water was then tested and showed no calcium or magnesium. On May 14th the other snail started to move slowly. The first snail (light colored snail) died this morning. The dark snail is still moving around but not much. The shrimp looks strange, but is acting normal. I will add the Rift Lake on Monday when I can be home all day to monitor.
I feed the fish New Life Spectrum Optimum Flakes and the shrimp an snails New Life Spectrum Invertebrate Crustacean pellets. I occasionally will give them a New Life Spectrum Algae wafer or a Hikari sinking wafer because everyone seems to like those.