The article itself mentions that the conditions are dire:
"They have central demands and will continue to fast until they achieve them. The prisoners see hunger striking as the only door they can knock on to attain their rights," Amina al-Taweel, the centre's spokesperson, told Al Jazeera.
"Even though it is one of the most dangerous and difficult decisions, they are only making this choice because conditions [inside the prisons] have reached a new low," said al-Taweel.
What are these "basic rights" that the prisoners are demanding?
Adding satellite channels "tailored to the needs of prisoners"
Restoring classes at Hebrew University
Installation of a public telephone in all prisons to allow communication with relatives
Allowing second-degree relatives to visit
Allowing children and grandchildren under 16 to visit
Increasing duration of the visits from 45 minutes to 90 minutes
Allowing prisoners to take photographs with their families every three months
Installing air conditioners in prisons
Restoring kitchens for use by prisoners under the exclusive supervision of the prisoners themselves
Allowing detainees to keep their own books, newspapers and clothes that families bring
Ending solitary confinement