I'm getting some slight PTSD watching Horford in recent games. I still love the guy and know he's in a tough spot with Porzingis injured, but even last year's postseason we saw signs of slippage and bad play from him which we're not accustomed to. For me, it wasn't just getting attacked defensively, but the guy had six wide open 3s and bricked them all.
With that said, I agree with tonydelk. Since Game 1 of the MIA series, they haven't really had any "awesome" games shooting from 3. They've had a few solid ones, some awful. They do feel due for a big 3-point night, where everyone chips in and guys like Horford are also cashing in with their opportunities.