Mixing RO and tap is the easiest way. I'm still not sure I understand why you need to alter it? Is it just because you want to?
The problem with chemically altering your water is that there's a chance the parameters will fluctuate between each water change if you don't measure/mix precisely. Stable water parameters with your current pH and hardness are better than shifting parameters that sometimes occur when you're trying to lower pH/hardness. This is especially true if you are doing large water changes.
You also have to take into account the buffering capacity of your water. If it is high, peat, leaves, and wood won't do much unless you have a lot to break the threshold. In my water the KH (buffer) is high and I have driftwood and used leaves and other things and saw no difference really. However, when I added a DIY CO2 contraption the PH lowered from 7.6 to about 6.8-7.0 . When you mess with the PH you need to know what you are doing or you can expect fish to die. It is best to have stable PH rather than a specific PH. Only reason I used CO2 was because I was using it on a planted tank and it brought the PH down. I also ran a bubbler at lights out with a timer to balance the CO2 concentrations.
Are the leaves yellowish? I'd try some type of iron supplement
What's the substrate and lighting?
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I'd upgrade your lighting, unless you want all java fern and anubias. My rams spawned on my amazon sword leaves and smooth rocks.
When you say you dose flourish, are you dosing the entire line: trace, iron, excel, nitrogen etc?
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