No one can downvote your vote power. Only your post payout amount.

Your voting power is apx 50% right now. You can recharge appx 10 full power votes in 24 hours. You've pretty much upvoted too much for it to recharge. If you don't vote for about 2.5 days it will fully recharge.

There is a chrome extension that helps give more information, like vote power, vote value, the amount that other people have upvoted your posts, etc. I find it helpful for keeping track. https://chrome.google.com/webstore/detail/steemit-more-info/dcbpmclnlapbkgkddhencielibcjogcf