@Lilliwyt
This contain spoilers since you asked for it.
It still make sense, there's lots of chapter because mostly it's filled with this tournaments arc.
Nagisa played against Connie but she forced to withdraw from the match due her leg condition.
There's a hint that she'll make an appearance in world championship .
There's some artstyle changes from volume 4 onwards. Unless you followed up the story from there , you may see some Charater looks really similar. I kinda miss the first 3 volume art though and the fluff.
No one know about Ayano mom's status yet.
It might be just that her body cannot play badminton anymore due her age or just overtime strain, not cancers/illness.
Ayano is a genius because she was trained by her mother in childhood and carried the seed of Ayano mom's talent.
I don't know why you see Ayano as someone who can beat anyone without effort while she was badly get rekt against Nagisa and have to train from scratch.
Don't watch the anime, they butchered some Charater backgrounds to the point Ayano mom's is all at fault.
And the Reason why Ayano mom's left (Mom of the year everyone) were because she thought it would be better if she discover the joy of badminton by playing with someone around her age and not bound by herself anymore.
She Ironically trying to raise or adopt another child such as Connie for God whatever reason she has and never returned house for whole 2 years. (Anime makes it like she ditched Ayano for more than 3-5 years)
Ayano mother clearly said that she didn't want to force Ayano play badminton but as she carried the seed of her talent she can't help to train her.