I transplant by up potting at least 3 times, and most plants 4.
I don't get this "drooping" plant thing. Yeah, I've seen it in some others operations but, I simply wait till the roots are starting to coil the bottom of the pot. Then you up pot.
Sometimes they coil a bit more then I would like. I simply take a blade and score an "X" on the bottom of the root ball, and up pot.
I have yet to get droopy plants, even after cutting the roots in that way. (BTW) That is an old school greenhouse trick to get the roots to spread faster..
I always use a simple water and kelp extract mix to the first watering at up potting.
I'll bet you up potted too early.... Let them roots grow out. All the way out, and then up pot.