Is it normal for my sisters to suddenly cut contact with me?

My 2 sisters and I have always been close throughout our childhood, and have many happy and enjoyable memories together. We spent most of our time together grew close. As we grew up we moved in different directions in life and had some ups and downs however we still maintained contact throughout these years. I am now an electrical engineering student, my older sister is an English major and the younger one is a 1st year humanities major.

However in the past 6 months Ive notice that my sisters have stopped talking to me, and have generally cut themselves out of my life seemingly for no reason I can think of. For example: untagging themselves from family photos I add on facebook, not calling me on my birthday despite me sending them cards etc.. Recently one of my sisters got facebook and added all of our family members quickly (cousins, uncles, my parents, my brother) but she hasnt accepted my friend request and its been 3 weeks. The other sister recently moved to the same city as me to start school but has not contacted me or replied to my offers of showing her around town/getting coffee. She also untagged herself from a family photo I added on facebook. They make me look stupid on facebook when they are all chummy with other family members but cant be bothered to accept my friend request/be shown in a picture with me. I dont have any rude or offensive things on my facebook page, mostly just pictures of electrical lab work I've done, group photos with friends etc..

I cant for the life of me figure out why they are being so aloof and passive aggressive this year. There was no recent fight, or major event. The only other time they distanced themselves from me was in 2005( I was 14) after I developed depression (lost 2 friends in a car accident). The depression made me not so pleasant to be around because I isolated myself, neglected my hygiene, and stopped doing basic things like washing my face, removing garbage from my room. They took it very badly because they thought I was doing it out of laziness. After 2 years I recovered from depression and we made up and got along again. Fast forward 8 years: I am 22 and have my shit together in school, and am well liked socially, and I no longer neglect my hygiene and my living space. Its not like I did something to drive them away since I am fully recovered from the grief issues.

Besides the depression problem from 8 years ago there is no reason I can think of thats making them cut contact. I am getting angry because I think they are being passive aggressive, cowardly, and downright rude by not giving me at least a reason why they stopped talking.