The test kit that you have is good enough for now for sure
you need to raise your Ph to 8.1-8.2 for starters you can pick up a buffer at any LFS.
then i would see about setting up a Quarantine tank and taking a few of the fish out of your tank for a few weeks
make sure to USE YOUR TANK WATER not new water because there will not be any bacteria in it.
and add new water to your tank.
leave them out for about 4 weeks
a rule of thumb that i use is pretty simple when adding fish or any type of life to your tank
buy yourself one or two every payday
(makes it feel like its worth going to work for
your amonnia and nitrates and nitrites should all be 0
how big is your skimmer?
it should be rated for more then the capacity of your tank
if its too small it will only slow down your tank
and water flow is a major thing you need a couple power heads to aerrate the surface of the water.
hope that helps any other questions please keep em coming