Rummy Nosed Tetras Acting Strange!

[Mikaila31]

I bought 6 rummy nosed tetras about a week ago, they are still in quarantine and I have noticed some odd behavior. During the day they act completely normal and it is the same at night. Yet, when I turn on the light in the morning two of them suddenly start swimming almost vertical with their head at the bottom and there tail pointing up. Another one starts to turn slightly on his side. This lasts for about 2 minuets then they start swimming about and acting normal again. Is something wrong with them or is this just the way they wake up?

The tank is 15gal and water stats are: 0 ammonia, 0 nitrite, 30 nitrate, and 7.6 ph

Thanks,
Mikaila31