There is this thing called The "
The Project Management Triangle - Time, Quality, Cost"
For content creation on YouTube,
- Time - How long it takes to complete your project.
- Quality - Researching/writing/editing your videos.
- Cost - the budget set to complete the project
You can't have all three corners of this triangle to produce a video, you can only pick two of the corners in this example.
In the case of seeing a decline of viewers on your channel, you are quality to produce your videos, as I assume you are a one man show. so your points on the triangle are fast and cheap, which would end up in a lower quality video, and people don't want to watch a low quality video. If you want to keep up with the 1-2 day uploads you would have to increase your cost to produce your videos, however if your not making money back on your videos, it's not a smart idea to pay too much into your videos. right now, your only cost are your time and equipment to produce your videos (i'm not sure if you have hired a researcher/writer/editor).
Now for what koala said, about if your sub misses a video that you uploaded, make sure your content is SEO (search engine optimization) so you can get some organic viewership, also known as people who are not subbed to you who are looking for content, can find your content, that way when a sub misses a video, someone else who isn't, can find your content and offset your views from your subs not watching your content.
Hope this helps, feel free to message me if you want to talk about this more in depth or have question.