I lost two cardinals and one galaxy rasbora today. They looked a little bloated and pale. Please see my profile for my stocking list. My params are as follows: Nitrate <10, Nitrite 0, Ammonia 0, ph 7.2-7.4

I was in a bit of a rush when I noticed them dead... I work at a daycare next door to my house and I had to get back to work so I didn't have time to take pictures. Any thoughts?

P.S. I don't overfeed them so I'm not sure why they were bloated... :(