Weaker than usually/recently...🤔

Hey, short question, has anybody experienced the same thing? Today, during my workout, I wasn’t able to use the same amount of weight I know I can normally lift. I’m anyway a person who’s getting stronger pretty slowly (I add more weight maybe every few months only. Which is okay for me, I don’t want to break any records besides my own 😉 The main thing is that I get better at all....) But the tendency should still be to become better, of course, right?... To either do more reps or to feel it’s a little bit easier over time and eventually to be able to pick heavier weights. But today, during my upper body workout (I currently do fb flex alternating with fb booty), I was not able do the number of reps that I could lift before with “my current” weight (same exercises). I felt like i had the strength 6 or 8 months ago or so. I definitely did 10 reps of overhead presses two weeks ago and today I couldn’t lift the same weights up 7 times, even though I already picked 3-4 pounds lighter per hand. Anybody had the same issue before? I’ve been consistent and didn’t have a long break (trained at least twice a week), and I even had two good meals (breakfast and lunch) today, enough water, there’s nothing I can think of that might have caused this. Besides maybe the fact that I had like 2 hours less sleep last week I must admit but I can’t estimate how directly that would possibly have an impact 🤷🏻‍♀️.... If my last upper body training was like 36 hours ago I would think today’s WO was too early but last WO was 4 days ago. I know we are humans, not not robots and maybe next time everything will feel “normal” again but I’m a bit irritated. 🤷🏻‍♀️ So, did anybody else have similar fluctuations in effective strength so obviously?? (Thanks already. :) )