I enjoy your tank. Its so clean and clear. We are our own worst critics. Your couple little spotty leaves are nothing. The plants look great.
As far as the flow, I think you have plenty. Yeah, the plants don't seem to be swaying in that corner as much as the others, but I don't think the water is stagnant. Just not enough to move the plants around like you'd like.
I got one of those Eheim suface skimmers recently for my tank. Maybe would be a good addition to your 20. I had a terrible time with gunk on my water. This has been one of the best purchases ever. Now if I can get rid of the green water.