I think what made them sound worse are the lack of proper vocal exercises needed when they did their solos.
An on/staff vocal coach is part of the artist management services that (in my layman's opinion) SC should have been providing for their singers, so they stay in shape vocally and work out developing issues quickly to limit the risk of deterioration.
unlike Sakurada who knows how to truly blend with the band and vocalists.
I've seen Sakurada catch some strays in this forum but he's an excellent player. Always in sync with the flow of the song and adds small, beautiful flourishes, though in a similar yet different way than Kajiura.
His playing during one of Hikaru's lives where he supported her made me appreciate him even more.
Wakana's solo repertoire very rarely demand the use of her head voice,
Good point. So she's out of comfort zone with the requirements of her voice in many Kalafina songs, increasing her anxiety on those high notes, which also affects her singing.
What she has gotten better at is vocal dynamics and emoting which she doesn't incorporate into her "Kalafina singing" for some reason. Not singing everything in forte would lessen the strain immediately.
I think Wakana relied a lot more on her tone for her impact and just sang from her heart, but her skill is definitely improved (minus head/falsetto range).
I have a feeling Hikaru has nodules based on the excessive amount of air in her upper chest range, which indicates a lack of proper vocal cord closure, a clear sign of vocal nodules. I don't think she has gotten surgery either from the sounds of it, perhaps due to the risk of making her unable to sing entirely like it did to Julie Andrews.
I completely agree with you. Hikaru is probably going against advice I would imagine she's received to do the surgery (what would be worse is if she did it and were seeing unintended effects, but I don't think so.).
For comparison, Saiki from Band-Maid also almost lost her voice when she got nodules (because of touring and an untrained voice belting high notes in a hard-rock connect) and her voice was scratchy and fading away. The surgery (and lots of rest) saved it and she learned how to sing with her voice and became the Saiki of today.
Her problems are stylistic, not technical, when she gets too excited during energetic songs and especially her "cutesy" voice when she raises her larynx to the roof.
I also agree with this. That's commensurate with Kaori's unnecessary yelling tendencies (also due to excitement) which lead to her going off pitch. Though, I'd say Keiko needs to work more on her mix mask placement in addition to her natural resonance (not low larynx) to be able to cut through the mix more easily, like say Emiko. Don't get me wrong, she's definitely improved from her Kalafina days, her early solo live, and even her Keiko's Room covers.
Keiko is the most improved singer out of the three of them, in my opinion, not just because her voice is healthier. There was a live on her YouTube before the 2025 reunion where I was impressed with how she sang a solo section with the others around her. Can't recall the song.