something to note; you don't need to add bacteria--unless you just filled up a new pond, you already have what you need. Even a newly filled pond will grow the bacteria you need; the question is how quickly. It's the bacteria you want to break down the ammonia into nitrite. Then, a different bacteria breaks nitrite down into nitrate. THAT'S when the plants come in. If you're going to go LPS (larger pond syndrome), save the current liner and anything submerged in the pond. If you keep these items wet, the bacteria and biofilm ON the liner and submerged items, you have the start you need. Also, keep the filter material moist as there too, you have bacteria. Buying bacteria is only a waste of your money.
You may be able to keep your goldfish but you're going to have to increase your filtration to keep up with them. Consider making yourself a bog (upflow wetland) filter. There are many threads here to inform you; just do a search. Going larger, if you can, will help immensely because the larger the body of water, the harder it is to throw the water parameters out of whack. Yours is indeed small so 7 larger fish are going to make it difficult. You've got basically 20 gallons per fish and as stated above, one inch of fish is relative. Goldfish and Koi tend to be heavy on the bioload, so your filter needs to keep up.
And as Lisa stated; stop putting all the chems in. Most of the time, that's when we hear the horror stories. In the 10 years I've had my pond, I've never put anything in the pond, chemical-wise. I have a well and don't even need any dechlor. Plants, lots of them, aeration (bubbler or waterfall or pump), and not overfeeding, are your friends.
And if you're getting a new test kit, as noted above, make sure it's not the strips, which have been proven to more often provide false readings. API makes a kit we all tend to promote. That said, I've never done any tests, either. I've kept tropical fish my whole life and I usually just watch the behavior of the fish to decide if there's problems. Of course, as you'll find out, ponds and aquariums are not the same.
Hope this helps.