I lost pez today from dropsy, and now 2 more are getting pine-coned.

How can I stop this from going through my whole tank? any treatemnts that I can do on the whole tank? Im so at a loss for what to do right now.

Test Results for the Following:
Ammonia Level? 0
Nitrite Level? 0
Nitrate level? 5
Ph Level, (If possible,KH and GH and chloramines)? 7.6
Ph Level out of the Tap? 6
Tank size (How many Gals) and How long has it been running? 125, running 2 months with fully cycled filters from old tanks.
What is the name and size of the filter/s? 4x aquaclear 110
How often do you change the water and how much? 50% once a week
How many fish in the tank and their size? 10, all over well over 6 inches
What kind of water additives or conditioners? stress coat
Any medications added to the tank? no
Add any new fish to the tank? yes, been qt for month
What do you feed your fish? flakes, worms, pellets, etc.
Any unusual findings on the fish such as "grains of salt", bloody streaks, frayed fins or fungus? pineconed scales, puffy bellies, pale color.
Any unusual behavior like staying at the bottom, not eating, ect..? not as active

Its a bacterial condition that affects the kidneys so there is something wrong somewhere for them to go down with it one by one.
Getting to the cause though is the difficult part as is treatment.
Have you tried upping the temperature and adding epsom salt?
If you have a spare tank then take out the fish you see with it and raise the temp to 80f and add epsom at 1/8th of a teaspoon per gallon and see if that helps.

I would now concentrate on tank maintenance and do water changes of 40% three times a week with gravel vacs and take out any ornaments and plants where dirt is collectiong to stop bacteria having a chance to build up.

I dont think you should add any more fish if you lose any for a long time after the last dropsy has been seen.

I know you have a 125 gallon tank with 10 fish, but with them being that big I would have said the stocking should be more like 15-20 gallons per fish.

How is the fish doing?