Normal fluctuations are common and expected. It could be natural variance, or it could be other factors such as you not eating well, not getting enough sleep, not in the mood for chess, or other "human problems." All chess players experience ups and downs from these human reasons in addition to mathematical variance.
Here is a video I made a while ago to help minimize the downswings:
I don’t understand it’s just so weird
I’ve dropped from like 950 to 841
It’s actually depressing and I don’t know what to do
And on an alt account I beat every 1k
So idk what’s happening