First off, dont get mad at anyone!
There are several things that could be going on in your tank to cause water clouding. I couldnt tell you all of them, but I'll give you a little advice based on my experiences.
You could be experiencing an algae bloom. You say your plants are growing like crazy and you have
CO2 installed so I would say that, with your lighting, your due for an algae bloom. Those come on rather unexpectedly, and you really cant predict when its going to happen so just let it ride and it will subside. There isnt a chemical that will make it go away any faster and you wouldmt really want to add any nasty chemicals to your tank anyway. I've tried and failed. The two blooms I've experienced only lasted a few days, but each time it happened when I was expecting company and wanted my tanks to look pristine.
There are several other things that could be going on, but we dont know the tank's age, so we would have to make many assumptions. Lets just start here; Regardless of the possibilities, lets take care of the basics first. Make sure there are no dead fish or plant matter in the tank i.e. remove any decaying material. Perform a good water change if you havent already....30 to 50 percent right off, then do 20 to 30 percent water changes daily for a little while....if there is something bad going on, we want to keep the water in good shape for the inhabitants that have to suffer through it.
Your tank is pretty heavily stocked, so keep up with your water changes; weekly 20 percent changes should be routine. Those plants will help tremendously!!!! I would like to mention that I think 3 dwarf puffers in a 15 gallon community tank is extreme. I would never tell anyone they are wrong for doing something, but I think its important to understand the possible outcomes. Although Ive never kept them, it is my understanding that you would not want more than one puffer in the same tank of that size. It seems to be working for you for the moment....cool.
Relax on the feeding schedule for a few days. In fact, your fish should be fine with no feedings at all for 3-4 days. More than that, really, but lets just see what we can do in a few days.
In review, Clean old matter from the tank, perform your water changes!!!! reduce feedings and wait for a few days to see how it goes. You should consider investing in a water paramater test kit...the results could help us pin-point whats going on in your tank.
The best advice I can give you is to keep updating this forum with your progress, because there are many, many people with wonderful advice and many have so much more knowledge than I do. I just have a love for the hobby and the people on this site that have helped me from the beginning and I felt compelled to say something to ease your mind just a bit. I know there is so much more I should tell you, but lets go one step at a time. Let us know whats going on, please! There will be many others with great advice for you, so check back often! Good Luck!!!!