Hormonal changes is exactly what it is. I tried all the ways to boost supply in vain, teas, cookies, supplements, motilium, but it's the pregnancy that dictates the hormones and causes milk to go. Doesn't happen to everyone, but it's not really controllable if it does happen to you, which really, really sucks.
With tandem, I assume you just feed the other child when the newbie isn't on the boob? And maybe off the same side the newbie had last? No idea lol

