Try to realize that your body's been going without these foods for a month, and springing them back into your diet is bound to have some effect. Sometimes that effect is basically unnoticeable, and other times it's blatant.
Also realize that our pre-Whole30 bodies were accustomed to living in a state of constant distress. We were used to always feeling some kind of discomfort, of some sort or another, whether we had a "reason" label to slap on the effect or not. Once we've done an elimination diet like Whole30, though, our body is "cleaned" of many things known to cause irritation/distress to many people. This means that if one (or more) food groups removed was causing distress, then you're going to see a much bigger sign of it now that you're reintroducing.
Think of it like a pool of water. If there's a machine making waves at the far end, and you're feeling them hit against you, then you might not notice (as much) when someone jumps in the water nearby... it's just going to send more or slightly larger waves your way. But if you're in a perfectly calm pool, then someone jumps in, the resulting splash and/or waves will seem much larger and more noticeable. The point of the elimination phase is to make our system like the pool of calm water, and reintroduced foods can definitely cause some very noticeable effects when you're starting from a level baseline and are sensitive to them
Remember that the purpose of reintroduction is to eat Whole30-compliant except for the single food you're introducing back in, which should be eaten at all meals for one day (or two if you want to spread it out)... then it's back to compliant for a few days to make sure you've recovered from the testing before you test the next food (or group) by itself.
My suggestion would be to take good notes, get through the rest of your reintroduction. If you want to go back to the troublesome foods you already tested to have another go and see if continued consumption allows you to become accustomed to them again, then that's definitely an option.
However, a little tough love and hopefully a bit of a light-bulb moment...
If you had frequent brain fog with constantly low energy, bouts of anxiety and depression, and general overall ickyness... all of which vanished during Whole30... doesn't it make sense that there might be something there that you might want to continue avoiding, even if it's one of your favorite foods?
For me, it's dairy, specifically cheese. I grew up with an allergy that I started ignoring as soon as I could, despite the fact that I dealt with eczema as a result. I didn't care, I had my cheese so I was totally okay with the rashes, the itching, etc. Fast forward to my first Whole30 reintro, when I decided to test dairy just because I wanted to see what would happen... and I learned that it not only set off my eczema, it was also the primary cause of my life-long issues with indigestion (including heartburn and reflux). From that, I can say without any trouble at all that dairy is simply not worth it for me about 95% of the time... occasionally, I'll decide to have "real cheese" on chili or a burger, but generally only if I'm eating away from home. I've learned to make some truly delicious non-dairy substitutes that I can always turn to if I feel like I'd like to have something cheese-like (though I don't do that during Whole30 or any other time when it's about habits as well as the food itself).
You've gotten some amazing results, doing away with symptoms that I know (from experience) had to have been irritating and miserable... so take a deep breath and remind yourself that this is ultimately about your continued health and well-being, and that you're strong enough to make informed decisions based on what you learn about your body's unique sensitivities and needs.
Obviously, you're an adult and can make your own dietary decisions, but making informed dietary decisions is really what Whole30 is all about. We obtain information through our reintroduction testing so that we can use that information to decide what our ongoing food freedom should look like... to be able to say something is or isn't worth it, based on how we know it affects us.
I'm on day 31 and plan on staying for at least 60. I did weigh myself today not really sure why. I'm sure to just to confirm I lost weight. I have found myself being cranky at night too.
I don't have any idea how to introduce foods sorry. I feel like it's not a good idea for me right now . Maybe look at why are you doing 90 days, what is YOUR motivation? Mine is I have a really sensitive stomach. My journey started day after I came home form Roatan, Honduras after spending a week drinking and eating whatever I wanted. I spent most of my mornings either in the bathroom or looking for one. I've been eating very clean for over 10 years but the past couple years have just been laxed and I put on 15lbs. and always felt tired. I'm feeling really good eating this way.
I felt bored last week but I read somewhere to look up new recipes to spice this up. I love to cook so it did reignited my passion. Good luck and do what makes sense to you.