I've found a few links that will surely be helpful!
http://www.vlognation.com/vlogging-tips/
http://megoonthego.com/2015/02/favorite-vlogging-tips-tricks/
https://filmora.wondershare.com/business/vlogging-tips.html
If you'll be needing more, be sure to search it up! You may come across a...
Here's what you should improve/add:
Better thumbnails,
Convincing titles,
Smoother commentary,
Professional descriptions,
Advanced editings,
CTA's,
Remove background noises.
Unfortunately, YouTube has changed verifications. Networks used to decide who's worthy of being verified. Although, nowadays channels have to have over 100k subscribers before they can be verified.
Basically, no networks can get you verified anymore, without 100k.
People are bored of your content. They just don't find your videos enjoyable. Look at what day you started losing subs and find what videos are receiving lots of views.
Obviously, people won't just find your channel ad videos just by joining a network and being partnered. You have to do something to make an impact on your channel.