I agree with many others, 1, 3, 5 look most suspicious (assuming numbers precede pictures)
Others seem to have heavy upscaling but it doesn't tend to become too patterned. In 1, 3, 5 grass tends to become something like a fractal rather than grass, plus reflections are sometimes off (that is why 2 is a bit suspicious because of a small tree reflection, but maybe it's just hard to see the original tree), and the branches tend to grow from multiple trees at the same time
0, very good, but I feel the grass on the bottom left is off (see comment on 6, probably real)
1, the dead grass on the right looks off
2, the trees to the top left look shifty
3, the dead sedg/grass in the center looks too even
4, might be real
5, the dead grass again looks off
6, same location and time as 0, either the same seed or real