artists i am following keep getting unfollowed

[sittingchrisey]

I have noticed this before but never done anything, but it has been happing for at least 4 months now. in the most easiset way to put this, i have been listen to the new trivium album alot recently and i just went on spotify to listen to it and they arent in my artists. not the first time. i recently re followed system of a down and scars on broadway too, followed them since ive been on spotify. i want to know why they are disapering when i am not unfollowing and for my followed artists to stay. if it keeps happeing id be as well going bk to free coz its not worth the cash if i have to re follow stuff every week 

[sittingchrisey]

just realised another artist that had dissapeared, lamb of god........... would never had unfollowed them 

[sittingchrisey]

help please?