In Signal, did Lee Je-hoon and Kim Hye-soo perform poorly?

I'm usually not very good at judging acting skills, but since the latter half of this drama drags a bit, the acting really started to bother me. Lee Je-hoon delivers lines with a serious expression and a furrowed brow, but it significantly breaks the immersion, and Kim Hye-soo has this feeling of constantly trying to speak elegantly with her eyes wide open? Honestly, I think Mr. Cho performed well in this.