Per las night's karaoke stream, Ruka will be reducing the frequency of her streams from now on, due to her throat. Her vocal cord, which was said to be very pretty by doctors 3-4 years ago, has became thicker due to overuse, and might be damaged if not taken care of properly (but in exchange, she can sing lower notes more easily now!)
In addition, her nose has enlarged adenoids and curvature of mucous membrane, leading to inflammation easily. Before debut, she did an operation on it, and that turned out fine. However, it remained a little inflamed > causes phlegm > goes into throat > more inflammation
Later in the stream, she also mentioned that the nose is the main cause and hopes it can be cured, and that we do not need to worry and to leave it to her, and she will go at her pace
this will not affect her streams or upcoming music performance plans, including *gasp* lives when she gets her 3D in future! So, not to worry at all!