This is not going to be easy, finding a "centrepiece" species comparable to angelfish. The main issue is the active swimming behaviour of Danio kerri [Brachydanio kerri in some sources] which I assume is the species "blue danio." Active swimmers tend to annoy sedate fish, and over time this causes stress. This may have been behind the angelfish issue though I've no idea what that was about, but inappropriate species do lead to other problems which may not seem at all related but are.
The best idea here is a third shoaling fish that inhabits the middle layer of the water column. The danios are primarily upper level fish, the phantoms primarily lower level, so mid-level could use a species. Thinking larger fish that would fill more of the "centrepiece" role as far as possible, the Bleeding Heart Tetra comes to mind. A group of seven or eight.
No mention is made of water parameters, so I have gone with what works for what you already have, assuming it to be on the soft to moderate GH side.