Firstly I'd like to say I appreciate everything you do and I'm posting this to show my appreciation by trying to help, not to be nagging or ungrateful 
I have a couple of things to note about the videos, and I'm happy to help with fixing both things if you want.
1) The colours vary between the SD version and HD version of the same video. The HD video's colours are more washed out/lighter and more yellow than the SD one, which can result in skin tone looking less good in the HD version. Your encoder or exporting program should have a colourspace option, if it does I recommend setting the HD preset's colourspace option to the same as the SD one.
For example, here is the SD version:
And here is the HD version (resized to SD):
2) The resizing used to scale down to SD seems to be of low quality and cause stepping artifacts. Using a softer resizing algorithm will fix it. If you want specifics for your program I'll be happy to help there too.
Here's the same pic as the first one above but with the stepping artifacts circled to emphasise what I mean. Also it should be noted that these are a lot more noticeable when the video is in motion since it looks like straight lines move, almost like watching interlaced content.
Compare to the second image from above, for which I used a softer resizer, and you'll see the artifacts aren't there and even the text in the lower right corner is more readable.
I have a couple of things to note about the videos, and I'm happy to help with fixing both things if you want.
1) The colours vary between the SD version and HD version of the same video. The HD video's colours are more washed out/lighter and more yellow than the SD one, which can result in skin tone looking less good in the HD version. Your encoder or exporting program should have a colourspace option, if it does I recommend setting the HD preset's colourspace option to the same as the SD one.
For example, here is the SD version:
And here is the HD version (resized to SD):
2) The resizing used to scale down to SD seems to be of low quality and cause stepping artifacts. Using a softer resizing algorithm will fix it. If you want specifics for your program I'll be happy to help there too.
Here's the same pic as the first one above but with the stepping artifacts circled to emphasise what I mean. Also it should be noted that these are a lot more noticeable when the video is in motion since it looks like straight lines move, almost like watching interlaced content.
Compare to the second image from above, for which I used a softer resizer, and you'll see the artifacts aren't there and even the text in the lower right corner is more readable.
