Personally, I think your upload schedule is fine. Since your niche is fitness and exercise and such, most people workout in the afternoon/evening. And during the weekdays, most people are too tired to workout. So ideally, for most people, I think Friday is the day that you can expect a lot of people wanting to focus on fitness. It's the start of the weekend, they already got that "work" momentum built-up and have been thinking of doing something other than work/school all week. And on Sunday, most people are just lazy. The thing about your niche is that it's less personality-based and more content-based. And what I mean by that is more people are going to randomly find your videos on a case-by-case basis, rather than watch every video just because you're in it. It's sort of like How-to videos and DIY videos. Like, you don't watch "How to build a birdhouse" because you think the person making the video is funny, you watch it cause you want to build a birdhouse.
That being said, your videos are kinda evergreen. Meaning, they won't generate a lot of views as soon as they upload, like say a channel like DramaAlert or Philip DeFranco would, since they cover news stories and current, trending topics that are only interesting the day they upload that video. Your videos aren't gonna spark a lot of interest immediately, but they won't die out. They'll constantly keep getting views, even though they don't immediately get them.
As for why you're getting less views immediately per upload.. I think that could partly be on YouTube's end. The site's constantly changing the algorithm and isn't very transparent with its creators. Gaming videos, for example, have been getting noticeably far less views this year than they have the past few years. And a bunch of bigger channels in the gaming niche, like Jacksepticeye, have commented on that. Part of it's changing audience taste, but another part of it is YouTube not promoting gaming as much as they used to.
A conspiracy that's been going around on the down-low is that advertisers are boycotting certain genres in order to force YouTube's hand in giving in to their wants and needs. Which I personally can see. Given recent media influence and YouTuber outrage, advertisers certainly have picked up on how much of an influence they have on the platform. And considering YouTube is a business, they'll automatically promote whatever content gets them more money. A lot of politics.
In conclusion, it might not be the day of your upload schedule. There are a lot of factors influencing views, and it shouldn't be too shocking to see videos posted a long time ago had an easier time getting views than current videos getting views. I kinda experience this, too. My current views per video are half of what they really should be.