Welcome to FishLore
Many times, overfeeding will lead to an algae bloom, which will make your water green.
The first thing you really should do, is read the link Lucy gave about the
nitrogen cycle.
Then,I would stop with the chemicals. A ph of 6.8 is in the range that most fish should be able to adapt to. (Usually anything between 6 and 8 is okay). What ever product you are using to lower the ammonia will only stop your tank from cycling and you'll be adding that stuff forever.
Once you stop adding the chemicals, you will probably need to start doing daily 50% water changes until your tank cycles (which could take a few weeks). I would recommend a product called Prime as a water conditioner to add to the new water you put in the tank daily. Prime will make the ammonia non toxic for 24 hours (at which point you will be doing another 50%
water change.) I would highly recommend getting an
API Master test kit, so you can monitor your ammonia, nitrite and nitrate levels.
If you can find a product called Tetra SafeStart, you could cycle instantly and it would make your life much easier. My only concern is that whatever ammonia lower product you put in your tank would stop the SafeStart from working properly. So even if using SafeStart, I would do water changes for a few days before adding it.
I know this post is long (and hopefully not to rambling), and probably a bit overwhelming but feel free to ask any follow up questions you may have. This is all very confusing in the beginning, but in a couple of weeks you'll be wondering why it seemed so hard.
So in conclusion (I know finally!) once cycled, the only chemical you should need is your water conditioner. Other than that, you tank should be self sustaining.
Good luck... fish keeping really is fun once you get established.