Help emergency!

[ch-b]

I got 80 gallon aquarium with 3 plants so far 1 anubias and 1 java moss and 1 valls i have in the tank 5 platys 5 mollies 5 balloon mollies and 4 guppies and 3 angel angelfish and 6 sword tails from 2 days ago i found 1 balloon mollie died but i didn't care a lot but now i woke up and i found 2 platys died and 1 of my guppy died also i did a test yesterday and all my parameters are good 0 ammonia 0 nitrite and 10 mg nitrate iam using sera test kit box for testing and my ph is 7.0 and my temperature is 29c as we are in the summer now and i can't get it down more and i have 1 powerhead atman that blows the water a little and make it move and 1 airpump 2 outles i don't think i have lag of oxygen but i see sometimes my fish swim at the top but not all the times what should i do guys please help me i feel like dying i paid a lot for my system :s so far

 

[Mebbid]

So the only sign something is wrong is that some of them are swimming at the top? There's no spots, discoloration, flicking, or any behavior that's out of the normal for them?

 

[Laser]

How long ago did you purchase the fish that have died? I'm not sure if you meant that you bought the fish 2 days ago or that is when they started dying.

 

[loachy dance]

Im assuming cycled and not a new tank?
It coulbe something viral, wait could it be an additive for the plants? Too much fert or co2?
Need a bit more info.