Ballroom e Youkoso

[Buffalobiian]

And her not synchronizing well is also Tatara's fault and Tatara did well to realize that he can only go by if he acts like he did during the Tenpei Cup. Especially since their training was obviously awful too.

If I'm not mistaken, the partner "follows" right? If the partner doesn't get a proper lead, she can't follow and thus they can't synchronize their moves. Even less so if that partner used to call the shots.
(or are you telling me during practice Tatara was the one leading?... he was clearly not)

During practice, you learn what you're supposed to do. Even without the leader, you'd know what you're supposed to do given you practiced your regime. The leader will simply set the timing during the actual dance. You know you're supposed to do a Spin A, Turn B and Flip C as per practice.

This episode highlighted everything I had in mind:

At this level, leading is everything. Tatara's lead is everything, and the ability to dance and win is also his full responsibility. They need to start back at basics, have Chinatsu dance basic moves to match Tatara, and forego competition wins if they have to in order to nail down the basics.

Isn't this tournament they are going to now several month "in the future" from where they were at 2 episodes ago or something?

It's 1 month post starting at Marisa's place, shortly after he rocked up. It'd be no more than 2 months post their D-Rank comp, I'd say much closer to 1 month.