RO KH/GH problem

[Branch]

I use, and have always used, 100% RO water with Tropic Marin 'Re- Mineral Tropic'. Although my PH is always around 6.8 to 7 which has been perfect for the domestic discus I'm concerned about the Wilds I have recently purchased, I posted on the feeding section as they won't eat whilst the domestics do. Checking all my parameters trying to identify whether something was off I found that my KH is less than 1 with my GH barely higher. Given that I've not changed anything and it's always been the same in this 10 year old tank does this low reading pose a problem? 50% water changes are carried out weekly. Any help would be appreciated.

[Kirbs]

I mix my RO/Tap water to 3:1. My GH is 2 and KH is 3 with TDS of 46. My wilds do fine. I would mix in some Tap to bring it up a bit. I also change 40% of the water twice a week.

[Branch]

Always felt a bit nervous about adding in our tap water as it's loaded NO3 and needs the chemicals removed. Will give it a check and see. Using the Re-Mineral by Tropin Marin increases the TDS significantly seems there's also a 'but'.. Thanks