Graphene

Hello everyone, first post on this forum. I would say I am relatively new to shrimp keeping, I've had my tank for a month now(just cherries). Before I changed my water yesterday, I had filled a 5G bucket with water and let it sit for 2-3 days, oh yeah I added API stresscoat to dechlorinate it too(honestly its probably chlorine free as I use well water). Anyways my tank is a 5G tank and I took out about 1G of water. Everything seems fine, actually the majority of the shrimps are doing their normal thing, however, one shrimp, a female, just swims from the left of the tank to the right, this is repeated over and over and over. I thought there might be something wrong with my water, so I did a test, here are the results: 0 PPM NH3/NH4 0 PPM NO2 5 PPM NO3 6.4 pH (the pH is probably low because my home water is run through a water softener, so there isn't much minerals which explains the low pH) These should be within the livable parameters of cherry shrimp, anyone know what might be up with this ONE shrimp? Thanks guys.