I noticed I'll gain 3+ pounds the next day after heavy leg day.....like clockwork.
What do you think is causing that to happen.
Training hard & heavy, shocking the body, maybe that why your holding water.
Types of food eaten before leg day, or pre workout mix, hormones natural or otherwise.
I don't weigh myself, so can't comment on any weight gain after leg day,
I notice I can't eat my usual sized meal after & split it in two.