That sucks @Treach1337
I am not sure how the system works. IE what level we start at. So treat anything I say as suspect 
I do know that recently the grading/rating system suffered a glitch. Maybe partially responsible.
I know I stick very very closely to the criteria and the recent glitch impacted me. At the same time I think that Emily (the ML AI that Niantic used) was processing most good nominations automatically so more poor nominations came in and my rejection ratio rose real rapidly.
There is a possible reverse to this and as has been suggested you were accepting more of these poor nominations and the rating system now recognises this. I don’t know.
But the glitches were reported a few months ago. So you may have come into the system while all this supposed lot of issues were happening
Dunno. But for instance I was great literally within months of starting - remained so for a couple of years and then - dropped like a stone. Only a few weeks ago did I come back to Good. And only after I only reviewed 100% perfect nominations. The first nomination that came up as not good - I stopped reviewing. Was that a factor in improving. Don’t know.
But @Treach1337 you are not alone. As Xenopus says triple check and use the criteria. Do not be afraid to thumbs down/reject… I find this Wayfarer forum quite useful if I have doubts Criteria Clarification Collection - Niantic Wayfarer Community
And this post on how for nominating and reviewing is pretty decent too Top Mistakes Made When Nominating, and How to Avoid Them
It is only a game. And our ratings are just a rating. Just keep enjoying the game and thank you for contributing for the wider Niantic community by reviewing. Appreciated
Good luck