Looks great! Nice greenery, and maybe a bit of color contrast (some redness) would be great too!
Regarding cardinals, I don't find them as fragile as people said. I have 20 in my 10G. Originally 30 but I give some back to my LFS. These 20 cardinals has gone through every tank mishaps from day 1. I think they vary from batch to batch, and luckily I have a good batch from the start.
I don't think transportation stress has that much to do with it. If these fish are from South America. The trip to US is much much shorter than the trip to Taiwan.
I also find them happier when there are a good number of them together. I've seen some other people's tanks locally where they only have a few of them (6 and under) in tanks much larger than my 10G, that are not doing too well either. So maybe the sheer size of the school contributed to their hardiness.