Blackwater extract will do the same as it's rich in humic and fulvic organic acids. Indian Almond Leaves (IAL) will provide a source of food for the shrimp. Peat moss will lower kH as well.
Your kH is rather high for a mix of 50% RO water. Make sure you do the test correctly. 10 dkH for a 50% RO water mix means you have at least twice that in your tap water.
If you don't want to mess with the above natural solutions you can dilute the tap more with RO water or go full RO and re-mineralize.
I'm keeping neos with full RO water. I'll probably never go back to tap water