I had 3 jumbo cardinal tetras for about 2-3 months, they were perfectly healthy. I decided to add 3 more so they could school. The day after I lost 2 of the tetras, one was dead dead, the other had a curved spine and looked like it couldn't swim. The next day 2 more had died, similar symptoms. It has been about 1 1/2 weeks since that with my two remaining tetras, they always seemed to be a bit restless, but I was hoping it would be because they didn't have a school. Now today I noticed a swarm of white bubbly spots on them, they are still restless, and a loss of appetite. I have 1 male guppy in the tank as well, and so far none of this has phased him. The tetras are still schooling together, as well as have a nice color to them, sometimes they calm down...but they seem very stressed.
Is this the neon tetra disease, false neon tetra disease, maybe ich? (although they don't seem to be itching against the gravel.) Is it worth me getting antibiotics for the fish?
EDIT: I take that back, my fancy guppy appears to be hiding by the heater, which is something I haven't seen him do. (he shows no physical signs)
Water conditions: 7.2 pH, 0 Ammonia, Nitrite, Nitrate. 78 degrees.