I'm not sure the panda corys would be happy at discus temperatures. I'd go for adolfoi (dark sand) or sterbai (light sand).
As for the tetras, I've had both cardinals and rummynoses, and my discus have pretty much ignored them all. It's more likely that the angels will snack on small tetras, but with cardinals and rummynoses you should be fine.
I do suggest you go for a single species, and if you do the rummynoses will look spectacular.
I wouldn't stock angels and discus together, it is something that is not recommended.
Also 4 discus isn't a recommended number, they are shoaling fish. You either have a pair or, much better, a shoal of at least 6.
The rams are fairly social animals, not as much as bolivian rams, but still... In that tank I'd go for three pairs.
Lastly your tank seems well overstocked.
I'd go for something like this:
x 7 Snakeskin Discus
x 18 Sterbai Cories
x 18 Rummynose Tetras
x 1 Rio Negro Pleco
x 6 German Ram
x 1 Whip-Tail Cat