Why was sarada sick? The answer

[Reviewing Logic]

or maybe like any other kid she had the flu

 

[Lyke]

Ramadan has ended must releasae all the shaitans U_U

Ramadan ends 26 afaik

OT: she is ill bcoz Sakura genes as Tauren said

 

[UnknownJin]

Dem Sasuke genes.

whats that?

-Sarada solos

 

[itachi4real]

All the bullshit and fanfic aside you have a point of her illness being related to her power. My opinion is the chakra she inherited from Sasuke was too strong for her body, part of the reason she has bad eyesight as well. I think it was likely the same illness that Itachi and Kimimaro had.

This seems reasonable