fish behaving strangely,

[vanilla]

Hi, can anyone help.
some of my fish are not well,we found a dead platie this morning,then one of our catfish was swimming upside down, did a water test and all is ok. now a tetra is swimming a bit odly. then after about 10 mins they are ok. is it the weather, we did a water change today.

 

[paulthegreat]

Not enough info.

 

[Tokis-Phoenix]

What are your recent water stats like ammonia, nitrate and nitrite? What temp is the tank set at and are the fish showing any other odd behavior like gasping at the surface or breathing heavily?