tetra school small

I recently bought some white skirt tetras and one of them is swimming all around very fast up and down the tank. I was wondering if this is odd behavior because she is the only one doing it. Is this normal? And if not what should I do to help her?

Hello, So I've recently gotten into quite a predicament, I bought 6 neon tetras from a store for my 10 gallon aquarium, and 2 have died already from either stress or disease. I heard that these fish prefer schools of 6 or more, but I cannot buy anymore of these fish (I fear I wouldn't be able to...