Not familiar with your substrate and whether or not it buffers, but guessing it does from the description. I wouldn't advise bumping your pH, since the tank is going to be an acid environment (0 dKH). Aqua soil tanks take much longer to finish the nitrogen cycle than your typical aquarium, and plants are likely using some of the ammonia you've added. Nobody excited to set up a tank wants to hear this, but I wait 3 months before adding shrimp to a Caridina tank these days. It's probably overkill, but patience being a virtue is truer nowhere more than in a shrimp tank. Besides the nitrogen cycle, aging a tank for longer allows biofilm and periphyton to establish and gives time for your soil to "mellow out" and stabilize. Of course, you don't HAVE to age your tank as long as I do, but it can only help their chances. Nobody ever lost shrimp by maturing a tank too long.
Nothing good happens fast in an ecosystem.