We'll ... He died:''(
Water perimeters are perfect, I haven't lost a fish in forever, and I had done a 40% water change too. I just think he might of been too shocked in the move. Every now and then fish just don't make it through the transition.
I may get an oscar that's a little more grown.
I'd throw in all the plants in off the bat. The plants help to clean the water and help provide oxygen to the water. You can probably add fish with TSS almost immediately. Just know the plants will throw off your tests a bit. My planted 10 gallon didn't read nitrates for near 2 months. But...