Help - GH and KH keep increasing!

[Crabnebula]

Can anyone advise me what could be increasing my KH and GH for the past 4 months? My tank setup is as follows:

30L planted tank, ADA amazonia substrate, very small section of fine sand, granite rock(advised by store it would not leach minerals and it has been in set up from the begginning), lampeyes, red cherry and amano shrimp, few snails, 100% RO water treated with microbe lift water conditioner (which does not noticeabley raise the water hardness above KH 1)

On a daily basis I add about 0.5ml of easlifes: carbo, ferro, potassium, fosfo and nitro. I was adding sera florena on a daily basis but was aware that this was increasing my KH and GH so now only add 10% of what I was on a weekly basis but still the water hardness most of the time are KH 8 and GH 11, which is less suitable for the plants in my tank and also results in a higher PH. My rotala wallichi has been struggling in recent months.

I do RO water changes at least once a week ,sometimes more, of about 30% and I have had my tank for about 1 year. I want to avoid doing more water changes every other day to keep the water soft.

Could it be the fish food making the water harder, I use various flake foods and granules, or anything else?

I could live with the harder water and change a few of the plant types, but would like to understand what I am doing wrong?

Thanks

[aznartist34]

It's the rock

[acitydweller]

Perform the acid test on the stone to verify if it is in face leaching minerals into the water column as it would appear that the tank is buffering to some degree. Foods would not normally alter the gh and kh.

[Crabnebula]

Thank you, I have samples of the rock so will perform the test. Frustrating if it is the rock as it is covered in moss and plants, it is really integrated in the landscape, but I can start again if necessary.