Honestly, your serving motion looks good. Perhaps put a bit more drive into the ball using your legs and you'd generate more power.
One thing I noticed is that your ball toss for the last serve was about 1 foot more in front of you than the previous serves. Play the video and put your mouse at the point of contact for your first serve in the video. The next ones are exactly the same. But the last one is noticeably out in front more.
All in all, there's nothing wrong with the motion. It just looks like you need to be more consistent with the toss and find a contact point that works for you.