I was a patient with heart failure and hospitalized for several days. The discharge from the hospital provided written instruction saying weigh yourself every morning and if there is a few pounds gained over night to contact the doctor as that could indicate being in heart failure mode and fluids were backing up into the lungs and/or peripheral locations... the heart would not be strong enough to output the amount of blood received from the lungs. .
I can't provide any advice, but I have provided an insight into the possibilities with a quick weight gain and the possibilities. Your doctor (nurse) would have your current health conditions, medication, etc. and be in a better position to determine the significance if any.
Hope this helps, and if you have any further questions or comments you are welcome to respond. Take care.
Ken