Just an update that I've investigated this, and J's followers were not all added on 1 day - they've been added a few day over months - here's a date stamp for when each follower was added:
"DATE"
"Mon May 25, 2015"
"Tue May 26, 2015"
"Tue May 26, 2015"
"Tue May 26, 2015"
"Wed May 27, 2015"
"Thu May 28, 2015"
"Thu May 28, 2015"
"Thu May 28, 2015"
"Fri May 29, 2015"
"Fri May 29, 2015"
"Sat May 30, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Sun May 31, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Mon June 01, 2015"
"Tue June 02, 2015"
"Tue June 02, 2015"
"Tue June 02, 2015"
"Tue June 02, 2015"
"Tue June 02, 2015"
"Wed June 03, 2015"
"Wed June 03, 2015"
"Thu June 04, 2015"
"Fri June 05, 2015"
"Fri June 05, 2015"
"Fri June 05, 2015"
"Fri June 05, 2015"
"Fri June 05, 2015"
"Fri June 05, 2015"
"Sun June 07, 2015"
"Sun June 07, 2015"
"Sun June 07, 2015"
"Sun June 07, 2015"
"Mon June 08, 2015"
"Tue June 09, 2015"
"Wed June 10, 2015"
"Fri June 12, 2015"
"Fri June 12, 2015"
"Sat June 13, 2015"
"Sun June 14, 2015"
"Sun June 14, 2015"
"Mon June 15, 2015"
"Tue June 16, 2015"
"Wed June 17, 2015"
"Thu June 18, 2015"
"Thu June 18, 2015"
"Sat June 20, 2015"
"Sat June 20, 2015"
"Sun June 21, 2015"
"Sun June 21, 2015"
"Sun June 21, 2015"
"Mon June 22, 2015"
"Mon June 22, 2015"
"Tue June 23, 2015"
"Tue June 23, 2015"
"Thu June 25, 2015"
"Thu June 25, 2015"
"Thu June 25, 2015"
"Sat June 27, 2015"
"Sun June 28, 2015"
"Sun June 28, 2015"
"Sun June 28, 2015"
"Mon June 29, 2015"
"Mon June 29, 2015"
"Mon June 29, 2015"
"Tue June 30, 2015"
"Tue June 30, 2015"
"Wed July 01, 2015"
"Wed July 01, 2015"
"Wed July 01, 2015"
"Thu July 02, 2015"
"Fri July 03, 2015"
"Tue July 07, 2015"
"Tue July 07, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Thu July 09, 2015"
"Sat July 11, 2015"
"Sat July 11, 2015"
"Sat July 11, 2015"
"Sat July 11, 2015"
"Sat July 11, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Sun July 12, 2015"
"Tue July 14, 2015"
"Tue July 14, 2015"
"Tue July 14, 2015"
"Tue July 14, 2015"
"Tue July 14, 2015"
"Tue July 14, 2015"
"Wed July 15, 2015"
"Wed July 15, 2015"
"Wed July 15, 2015"
"Thu July 16, 2015"
"Thu July 16, 2015"
"Fri July 17, 2015"
"Fri July 17, 2015"
"Fri July 17, 2015"
"Sat July 18, 2015"
"Sat July 18, 2015"
"Tue July 21, 2015"
"Wed July 22, 2015"
"Thu July 23, 2015"
"Fri July 24, 2015"
"Fri July 24, 2015"
"Fri July 24, 2015"
"Fri July 24, 2015"
"Sun July 26, 2015"
"Sun July 26, 2015"
"Sun July 26, 2015"
"Mon July 27, 2015"
"Mon July 27, 2015"
"Wed July 29, 2015"
"Wed July 29, 2015"
"Thu July 30, 2015"
"Fri July 31, 2015"
"Sat August 01, 2015"
"Sat August 01, 2015"
"Sat August 01, 2015"
"Sun August 02, 2015"
"Sun August 02, 2015"
"Sun August 02, 2015"
"Mon August 03, 2015"
"Tue August 04, 2015"
"Thu August 06, 2015"
"Thu August 06, 2015"
"Fri August 07, 2015"
"Fri August 07, 2015"
"Sat August 15, 2015"
"Sun August 16, 2015"
"Sun August 16, 2015"
"Tue August 18, 2015"
"Wed August 19, 2015"
"Sat August 22, 2015"
"Sat August 22, 2015"
"Sun August 23, 2015"
"Sun August 23, 2015"
"Tue August 25, 2015"
"Tue August 25, 2015"
"Wed August 26, 2015"
"Wed August 26, 2015"
"Sun August 30, 2015"
"Mon August 31, 2015"
"Tue September 01, 2015"
"Tue September 01, 2015"
"Thu September 03, 2015"
"Sat September 05, 2015"
"Mon September 07, 2015"
"Tue September 08, 2015"
"Thu September 10, 2015"
"Fri September 11, 2015"
"Sat September 12, 2015"
"Sun September 13, 2015"
"Tue September 15, 2015"
"Fri September 18, 2015"
"Mon September 21, 2015"
"Mon September 21, 2015"
"Tue September 22, 2015"
"Tue September 22, 2015"
"Thu September 24, 2015"
"Sun September 27, 2015"
"Mon September 28, 2015"
"Mon September 28, 2015"
"Mon September 28, 2015"
"Tue September 29, 2015"
"Wed September 30, 2015"
"Thu October 01, 2015"
"Sun October 04, 2015"
"Thu October 08, 2015"
"Thu October 08, 2015"
"Thu October 08, 2015"
"Fri October 09, 2015"
"Mon October 12, 2015"
"Wed October 14, 2015"
"Wed October 14, 2015"
"Sat October 24, 2015"
"Sat October 24, 2015"
"Sun October 25, 2015"
"Mon October 26, 2015"
"Sat October 31, 2015"
"Sun November 01, 2015"
"Thu November 05, 2015"
"Sun November 08, 2015"
"Mon November 09, 2015"
"Wed November 11, 2015"
"Thu November 12, 2015"
"Mon November 16, 2015"
"Tue November 17, 2015"
So you can see there's certainly been a few days where shes had a few followers, but this looks "normal" to me.
How did you determine that all of the followers were added in 1 day? I think that is where we want to look as the display of information is probably incorrect.
Hope this helps!