Ms Hebble then either passed out or fell asleep, waking 10 hours later to find water flooding her bedroom and her two sons lifeless in the bathroom.
Expert psychiatrist Felice Watt, giving evidence at the coronial inquest into the boys' deaths, said although Ms Hebble had no documented history of postnatal depression there were symptoms of the condition scattered through her medical notes.
"Certainly the possibility that Ms Hebble suffered from PND after Malachi's birth... is supported by some of the medical evidence," Dr Watt said.
This "evidence" included loss of appetite, weight loss and sleep disturbance with bouts of insomnia, which could last five days, the inquest heard.
Ms Hebble had told medical staff at Graylands Psychiatric Hospital, where she received treatment in the days after the boys' deaths, she would sit up watching TV at night because she couldn't sleep and would lie to her family about needing to be at appointments to avoid them.
Ms Hebble's parents were also interviewed by staff and although they reported no significant change in her after her second birth, they did note she had become more "isolated".
"Mothers frequently feel ashamed of how they feel and how they are coping," Dr Watt said.
"This can be one reason why they don't tell others what's going on."
Dr Watt said many women and their families may miss the signs of PND, assuming they were "a normal part of motherhood".
"There are some indications that Ms Hebble may have experienced extreme anxiety in the days leading up to her children's deaths," Dr Watt said.
"Diagnosis aside, it is clear that Ms Hebble was struggling with the demands of caring for two children."
She said there may have been financial, relationship stress and stress from dealing with her older child, Dr Watt said.
But, how these stresses related to the tragedy "remains unclear," she said.
The tragic case had highlighted the situations "women who are isolated might find themselves in," she said.
"These women have been identified as being a high risk of PND."
Social support through health care networks, friends and family, was an important part of intervention and treatment for these women, she said.
"I think a lot of good work's been done, but a lot more work needs to be done around issues of stigma, shame," she said.
Dr Watt said she was unable to make a diagnosis without examining Ms Hebble herself.
A psychiatrist assessment of Ms Hebble conducted by staff at Graylands diagnosed her with "acute stress disorder," when she was discharged.
Following the boys deaths she was also deemed a high risk of suicide.
"Ms Hebble was distressed, highly traumatised and a risk to herself in light of this," Dr Watt said.
Ms Hebble was due to give evidence on Thursday, but has sought legal representation in recent days, which has resulted in her evidence being moved to Monday.