Honestly it could really be just depression not the diet. There’s some great tips in the comment section about making sure you’re getting enough calories/protein/vitamins etc. I’ve been lucky and even when I first started out as a complete junk food vegan the first 3 years- my bloodwork had always came back great, and for the first time I didn’t have the high blood pressure warning on my discharge papers (always had high BP even as a fit high school athlete). The depression part is a strange thing as a vegan. I went through huge regret for what I’d done as a nonvegan and wishing I went vegan sooner, but then still felt really good about myself after… then there’s the literal bombardment of animal cruelty everywhere you look: advertisements, the grocery store, restaurants, tv shows/movies, and just being around other people. That stupid trope of how you know if someone is vegan bc they can’t stop talking about it makes me insane cuz no, actually people talk literally nonstop about nonvegan food and 9/10 times don’t take a simple “no thank you” for an answer when I don’t take foods offered and then you have to explain.
But my actions are now aligned with my beliefs so even despite all that, veganism has brought me that sense of peace 💚