Proper KH, GH, and PH level for a planted tank?
Recently i have a major melt down (literally) of all the plants in my tank, they literally melted down to the stem after about 3 weeks and created a huge mess in my tank which I still trying to clean up. So I went to my local planted aquarium store (they specialize in aquarium plants and only sells fish on the side, the opposite of a typical fish store). I talked to one of the person who work there and they ask a bunch questions on the type of plants, substrate, water parameters, etc. And they think the problem is my water hardness. Our city tap water is very soft, with kH and GH both below 3 and probably in the 1-2 range (base on results from test strips from petsmart). He recommends me to use ADA Bright K to raise the hardness in my tank to make it more suitable for plants, and use an acid buffer to help lower and stablize the pH at the same time. However, after he learned that I am using seachem flourish and excel as fertilizer in my tank, he back away from the Bright K and told me the ADA product does not mix well with seachem and might create bigger problem if I use them together. Instead, he recommend me look at seachem's own product line for GH and KH, the seachem lab auqavitro carbonate and aquavitro minealize (they do not carry these as they are mostly only carry ADA product lines).
Anyone have experience using the aquavitro carbonate and minealize to raise kh and gh? Or have any other recommendation for raising kh and gh for my tank?
The store clerk recommends a kh of 3-4 and gh of 5-6 (or the other way around, I might get the two mixed up), and along with an acid buffer to keep water slightly acidic in the upper 6s. Any insight on the proper level of kh, gh, and ph?