Hi Mykids: Questions are always helpful and appreciated

I really want to figure this out.
It's a 5 gallon tank and I have one plant and a moss ball. I have well water. I did switch tanks after AquaticAustin suggested the sealant might've absorbed some meds. The heater and filter were in the medicated betta's tank and I'm still using those. Can they absorb meds too? It's hard plastic...? Is there any way to detox all this stuff? The filter media was new and so is the substrate. The snails don't really perk up after water changes. They sometimes perk up if I put them in a smaller bowl, but not lately. I do use Prime and was worried about overdosing it since I was doing so many water changes. I posted that question on here before, but everyone said it wasn't a problem (?). I never use more than the label says.
Today on my lunch hour I got water from work (municipal) and did a 60% w/c. I want to see if this water makes a difference. If it does, then I'll KNOW it's my well water. The ivory snail perked up immediately and began climbing on the plant with its tentacles out! :dance2: I was sure it was dying because there was no recoil at all when I touched the operculum. So that was a pleasant surprise. The blue one opened up a tiny bit more but not much else. However, when I was leaving the ivory one was back to closed up and floating.

Ugh, who knows. It's so baffling I can't stand it.
I have no problem bringing in water from outside sources if I have to. I just wish I knew for sure that was the problem. BTW, ammonia and nitrite readings are both 0. Nitrate is 20.
Will drastic changes in pH cause this problem? Mine is quite high at 8.4. I tested the water from work and it was only slightly lower. Since I'm sure Petsmart uses the same tap water I can't imagine their water would be much different. I could call them and ask, but I've gotten so much BS from those people that it exasperates me. I so wish I had a LFS around here!
Will keep you posted...