It may or may not be a coincidence, but here are some of the questions researchers would ask, if they were to investigate it:
For how long have each of these individuals lived here.
For each: when did symptoms start.
For each: what is the family history of autoimmune diseases.
Was there any precipitating event (illness, virus) that they can pinpoint as a possible place when they first started having symptoms.
Diet, including water.
Jobs, and possible exposure to a trigger in the work place.
and a whole host of other questions.
I think lots of people are getting diagnosed with MS..and other diseases..more quickly these days because of better medicine, the availability of equipment like MRI's, and a greater awareness of the need to seek medical treatment, early (Many of us rocked along for years with various symptoms before ever going to a doctor..)
...I am not a doctor, nor health professional, and don't pretend to be one, here.....