I understand the fact that broad statement like that makes no sense but considering he said he lost 2 platys, 1 cherry barb and 1 cardinal, I'd say he has way too any fish if they are all in that size range unless he has massive filtration.
I also figure he (or she) has given up on this post since he hasn't answered any of the questions posed about water stats.
no you are right rdd, there is a fair possibility this tank is overstocked.
however jumping down the OP's throat with posts just saying you have way too many fish and not offering any constructive advice, waiting to find out the facts or providing any reference sources for the OP to learn from will achieve nothing except scare off the OP or get their back up.
It's a common problem with forums IMHE, once a newbie to this hobby learns a bit about cycling and stocking etc they feel it is time to give some knowledge back, now that in itself is a noble sentiment and one i will always applaud. however sometimes the advice offered is based on a few broad statements they assume to be facts because they do not have the depth of knowledge.
now don't get me wrong, i by no means think expereinced members should have monopoly over answering posts or that newer members should not help. or indeed that someone is correct simply because they are more experienced. but sometimes i wish people would just take a step back and do a bit more learning before they jump in bandying around assumptions, it can do more harm than good.
I'm probably in for a flaming now for saying that, but it does get my goat a bit sometimes.
take for example these two posts
18 fish in a 14 gallon tank
this is not going to help anyone, no advice just a statement followed by a load of smilies
Thats what i was thinking! That is way to many in a 15gal tank. They will be stressed and that may be the reason they are dying! What fish are in there?
another post from a beginner, but commenting that the stocking
may be the problem but waiting for the OP's answer before passing judgement.
easy to see what will help and what won't