Fully cycled tank (with currently a 0 for ammonia, nitrite and nitrate).

Planted tank with 1 betta and 1 assassin snail.

About a week ago I got a very nice new plant that is very bushy ( can't recall the name) to go along with the 6 red cherry shrimp I was purchasing that day as well.

Since I have planted the tank, I have not done a water change and the following things have happened:

I only see 2 RCS, and I have only found 1 floating dead in the water. There is a good chance at least another one is hiding, but I am not sure. My betta doesn't look any larger at all. And I mean I look very closely to check and see if she may have eaten some RCH as a snack.

My plants have been thriving. That new plant I brought just grew two new stems so it is doing very well. Both my swords are thriving now as well.

My pH has risen from a 7.5 to an 8.5. I have no idea why. Maybe that is what killed my RCS? Should I do a water change? I've never had a pH problem before.. Is there something I did wrong? Obviously I threw off some kind of balance..

Help! Thank you in advance!