Yes, KH of just a couple of degrees is fine for soft water fish and plants. It is enough to keep the pH stable, as long as other things are stable. You could raise it a bit if you want.
GH of 10 is fairly high for soft water fish, and probably at the low end of OK for the Rift Lake fish.
My Lake Tanganyikan tank definitely needs some help.
Tap water GH and KH are pretty close to 4-5 degrees most of the time.
I use baking soda to raise the KH.
1 teaspoon of baking soda per 30 gallons will raise the KH by 2 German degrees of hardness.
I use Barr's GH booster or Seachem Equilibrium for GH.
Instructions are on the label.
I also have coral sand substrate, and add oyster shell grit to the filter.
On water change day I will prep the water ahead of time in a garbage can, adding enough baking soda and GH booster to make it match the lake.
Then, through the week, as the plants, fish and microorganisms use some of the minerals, the coral sand and the oyster shell grit stabilize the mineral levels. Stays really stable that way.