Your strumming sounds quite nice. As far as the sound, I couldn't detect any strumming issues, but from watching you, I can see you're a little stiff. But it's nothing to worry about. It gets easier over time. Just think "loose and relaxed" when you play.

I did notice one other thing, though, but it's something everyone does as a beginner. But the sooner you break the habit, the better off you'll be. Ideally, in regards to chord changes, you want all your fingers to move as one. Particularly when going from C to G (which is hard, for sure, as it involves moving every finger) I could see that you set your little and ring fingers on the 1st and second string first, then got your index and middle fingers situated.

If you can, I'd recommend spending about 5 minutes a day of your practice time really focusing on those hard chord changes. Take it really slow and try to land all your fingers in their place at the same time.

All in all, it sounds great, though! You're better than I remember being at 3 months. Keep it up!