I get the sense that you want to add products to your aquariums. Lol. It's fun, makes ya feel like a chemist, ya know?
BUT, it's kinda like adding ingredients to a soup. Once you over do it, it is spoiled and a lot harder to fix.
So, I would reccommend that you share more information about your tank. Freshwater hardness is usually measured in GH. Have you tested for that? How high are your nitrates.
Just because you have a low pH doesn't mean that your hardness is too low, it may mean that your acid level is too high- usually the case with large dirty cichlids.