Listless and more

Question
Hi!  My 10gal is setup with 4 zebras, 3 fem and 2 male platy, 1 pleco.  All had been doing fine until recently.  Have a few fry left, and thriving, from the oldest female.
Yesterday, I found that female in the bottom of tank dead as well as one zebra.  I just had to remove another zebra which was dying.  
The tank super clear, ph bal is good, plenty of plants and an extra stone along with nice cycling filter.  
Why is it my fish seem to be dying one aft another?  I have noticed:  listlessness, fish hanging about top more oft than normal.  I did recently (about 2 weeks) cut back on their feedings from 3x's to 2x's daily.
Any suggestions?

TIA!

Answer
Hi Bambi
How long has your tank been set up?  If it's within the past 4-8 weeks, it's probably going through the cycle process.  A lot of fish don't make it through that, it's very stressful for them.  Here's a great link with really good and easy to understand articles that explain that process for you, need to copy/paste:

http://freshaquarium.about.com/od/startupcycle/Step_5_The_Cycle.htm

Now another issue I see, with that pleco in there, you're tank is overstocked.  Depending on what kind of pleco it is, the common ones get up to about 1-2 feet long.  You're tank is too small for him.  You're best bet is to return him if he's still alive.  Even if it's one of the smaller varieties, he really should have a larger tank.  The zebras, are they the smaller zebra danios?  If they're the smaller ones, they should be ok with the platies, a tad overstocked but not too bad.  If they're the larger giant danios though, that would be too much.

How often are you doing water changes?  I usually recommend doing them once a week, and changing out about 25% of the water/vacuuming the gravel, for a normal stocked tank.  But if you're tank is cycling, you need to do smaller daily changes to help dilute the toxins in the water for the fish.  Then once it's completed the cycle, go on the weekly schedule.  Also, cut back on the feedings.  I feed my fish once a day, and even skip one or two days a week in there.  

Now, just because the water looks clear, doesn't mean the quality is good.  I suggest buying a test kit for ammonia, nitrite, and nitrates if you don't have one.  You're ammonia and nitrites should read 0 ppm, and nitrates under 20 ppm.  Anything other then that will cause the fish stress/death.  The symptoms you're describing: listlessness, hanging at the top, sounds like nitrite poisoning.  You can also use a bit of aquarium salt to help with nitrite poisoning, but the pleco may not tolerate the salt too well.  Again, I strongly suggest returning him though.

I hope all that helps!  Let me know if you have more questions!!  And good luck!

Christy