I've now found out:
Bright's disease 2[?] months [would probably be called acute nephritis today: en.wikipedia.org/wiki/Bright's_disease]
Rheumatic gout 1 year"Your kidneys filter uric acid, but if levels get too high or the kidneys can’t remove enough of it, [gout can ensue] ... Foods rich in purines, high alcohol intake, and drugs like immunosuppressants and diuretics can raise your risk of gout."
www.rosdrs.com/rheumatic_diseases_gout.htmlNephritis can arise from a UTI, immune disease, or strenuous exercise. en.wikipedia.org/wiki/Nephritis
From this it seems gout could cause nephritis, or nephritis could cause gout.
Martha's husband later died of alcohol poisoning so maybe that affected her health too. Besides that, in industrializing Newcastle I imagine poor hygiene could lead to UTI, or maybe a mother of 5 had unhealthily strenuous levels of physically activity.
That's as far as reason can take me, I think.
I've certainly been building a fuller picture of the poor living conditions in late-19th-century Newcastle through following this family. It must have been quite a shock for ordinary people/families to suddenly be in cramped streets next to factories. (Martha's family had moved in her childhood from the Bedlington Ironworks, much less urban.) Poor regulation of alcohol was a publicly-discussed problem as well.