I'd add to what I previously said that he seems to have a territory, while the others wander around. He doesn't mind others in his area, but he sticks to it generally.
Just ordered some of them, very excited, my first Sulewesi. I'm gonna name them all Loony.
My ph is 8.0 or so. I see many places that neocaridina are recommended to be at 7.5 or less, but I have had no problems.
The cardinal's behavior is different. It seems a little shyer in that it likes to hang out on the rocks beneath the wood "bridge," though it does venture out plenty. It will graze on the marimo balls and the wood, but it really prefers to graze on the slate best, and it has not shown any interest in the java or taiwann moss, unlike the others. It also is not interested in blanched zucchini.
Cardinals are not neocaridina. They need high pH. They are from Sulawesil lame Matano. It changes a lot
Your pH is good, but do not lower it.
Look here Cardinal Shrimp
Yes, I know. I have Neocaridina in the same tank with them, and I was saying that they (the blue pearls) do not have problems with the ph that high.