3 consecutive tiger barb s & black skirt tetras starving themselves

Question
I have a tank of four black skirt tetras, two sunrise platies and recently added three tiger barbs and one green one.. starting last night I found one dying.. the morning after one more and when i came home today the last normal tiger barb dead, I don't know whats wrong.. I just got my water checked today and it's fine, is it something to do with the ph or could the recent heat wave over here which is making the water temp in my tank rise?.. i really don't want the green tiger barb to die..

and one more thing two of my black skirt tetras seem to be starving themselves all the other fish are so eager to eat yet these seem to have no interest..

thanks
jobcel

Answer
Dear Isaac,
I'm very sorry to hear that...
My first thought would be water quality I noticed you mentioned you said the water quality was fine but please make sure the readings are as follows-
Ammonia-0
Nitrite-0
Nitrate-20 or less.

pH tends to not be such a big deal with fish unless it flucuates rapidly. The heat wave shouldn't have been a problem either. I live in a very hot area and unless the aquarium got unreasonably warm (above 85F) for a long period, I wouldn't say that is the culprit.
The majority of fish do fine at warmer than normal temperatures, as long as oxygen is adequate and it is for a short while.  How warm was your aquarium?

I would definately do a water changes of 30% or more and insure the replacement water is equal in temperature to that of your aquarium and that it is properly dechlorinated with a good water conditioner.
There could be something in the water that is affecting them badly and I would probably do this amount everyday until perhaps you see improvement.

Insure that no pollution has gotten into your aquarium of any sort (sprays, chemicals, cleaners).

Above all I would do water changes.
I noticed you mentioned your Black skirt tetras not eating. Sometimes these tetras can tend to be somewhat shy or reserved while the other fish eagerly eat. Try swirling the food in a aquarium safe (one with no soap or chemical residue) cup with aquarium water and pouring it in near the two reserved Black skirts, this usually tempts them but if not. I would imagine water quality may be the culprit.

I really hope this helps!
Only my very best wishes and Best of luck!
Karen~