OK, things are starting to make a bit of sense. Some of what I will now suggest will repeat prior advice.
First, on the plants. IF the initial GH of 60 is the tank, I assume this must be ppm [too high a number for dGH] and this equates to around 3 dGH. This is one major issue with your plants, there is insufficient calcium in particular and also magnesium. Walstad says the GH must be at 4 dGH or higher, and in my own experience with near-zero GH tap water this has proven true; my plants were falling apart until I used Equilibrium to raise the GH to 5 or 6 dGH and now they are lush and green. I'm not here suggesting yet more products, miksan, so bear with me.
Another problem with the plants is no trace minerals. API's LeafZone is only iron and potassium (according to their info online), and in your situation with soft water this is inadequate. [Iron in the absence of sufficient calcium is also deadly to plants, so another problem.] Plants need 17 nutrients. I would discontinue this product since it is not going to help and it is adding more TDS which stresses the fish. When it comes time to deal with the plants, Seachem's Flourish Comprehensive Supplement is one of the best complete ferts available; also Brightwell Aquatics' FlorinMulti. As a third option, though not as good as these, Nutrafin's Plant-Gro can help. But this is not "complete" and you use a lot more so it is more expensive plus not as effective--so it is only a last resort. These sorts of complete ferts will be sufficient in natural (low-tech) method tanks and are the easiest.
Last on the plants, the Excel again. This was actually making things worse for the plants, because the 17 nutrients have to be roughly in proportion. When something essential is missing, adding more of something else won't help, and often makes it worse, as here. You've stopped this now, but I just mention the balance so you know.
Now to the fish. Mikaila is quite right, there is far too much "stuff" going in this tank. I am a believer in
less is always better when it comes to additives, supplements, adjusters, etc. Every one of these is affecting the fish, by simply increasing the TDS (total dissolved solids). You have named fish for which this is serious, because they are soft water fish. That's one aspect. Second is, these products often don't do all they claim, or if they do it has side consequences; your example of the EasyBalance is proof--and this product I never recommend because it increases ammonia and that is likely some of what you experienced. Third, some of these may interact in a less-than-desirable way--think of it like medicines, your doctor always warns about taking multiple medicines and for the same reason.
Mikaila is also on the mark in that we need the numbers: GH, pH, KH of your tap water (not tank). Also, is there any ammonia, nitrite or nitrate in the tap water?
Bottled water: I don't know exactly what this may be, but bottled water can be dangerous in fish tanks depending what might be in it. If it is absolutely pure RO (reverse osmosis) water, then it will have nothing; but otherwise, no idea.
Water changes: When in trouble, do a water change of half the tank or more--provided the replacement water has similar parameters to the tank [see caution below]. I guarantee this is one of the best "cures" for anything because it removes so many pollutants and invigorates the fish. Provided the parameters are close, this is always a good idea. Use a good conditioner, one that deals with your source water issues and no more. Again, no need for more chemicals and stuff affecting nature if it isn't essential. In this situation, if you have Prime, fine; I would go with something more basic, such as one that treats chlorine/chloramine and not much else, but most will deal with heavy metals and that won't hurt here.
The caution in a water change is the different parameters. IF the tank water is pH 6.5 as first posted, and the tap is pH 9, this is too great a difference, so smaller frequent water changes are advisable to slowly adjust the tank.
I think I've covered the issues as I saw them, will check back later.
Byron.
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