Guys I need a bit of help here for a 24y/o 77kg 167cm female;

TLDR: Gained 5kg over a month and a half in weight while being in a deficit, cardio + resistance training, 10k steps (at least) and drinking at least 2l of water a day.

So, I started going back to Chloe back in September, I needed a bit of a kick up my butt regarding my weight and my mental health, and during lockdown, I lost 16lbs with Chloe, if not more. However this time around, of course I’ve gotten older, but I’ve also become more aware of my eating habits, my calorie intake and really decided to take it seriously.

Here’s the problem. I started back in September at 72kg, weighed in the morning. I weight myself this morning however, and while I don’t LOOK like I’ve put weight on, the scales say I’m up to 77.3kg. I can’t understand how that could be the case, as my calorie maintenance should be about 1900 from when I started, and I easily, according to my Fitbit, burn about 800 calories per workout, whether that’s doing Chloe’s programmes and a bit of cardio after, or just straight cardio on my rest days.

I can’t explain it, and many people tell me, “Don’t go by weight! Go by how you feel! How your clothes fit!” Clothes wise, everything fits the same still, nothing’s got tighter or looser, my mental health of course took a blow after seeing that, and with Christmas coming up, all the good food and stuff!

Any advice on what’s going on, would be amazing.
Here’s some photos from when I started, there’s not a massive difference because it’s only one and a half programmes in but, hey ho!