If those test strips are correct, your tank water is very soft. Honestly, I'd wait a little longer until your tank matures before adding inverts. Have you tested your tap water? It looks like the pH is being pushed down (possibly because of ammonia).

With your tank kh barely registering, your pH will swing easily. A little ammonia while you're tank cycled/cycles, kh gets consumed and pH will fall. I say cycles because the test strips show your tank is not cycled yet. If you just added the gouramis, there wouldn't have been much to add bioload.

It's normal for pH to bounce around in the start, that's why Slaphppy7 advised not too worry about it.

Test your tap water hardness pls and post the results. API liquid test kit is very reliable for what we use it for. One of the best things I bought for my fish.