As said above.. just tell them the truth.. and its not like you've done anything wrong. Just explain the matter to them and Im sure inshallah they will understand (you've been with them for over a year).
JazakAllah.
Asslmwalkm.
As someone said above eating with the right hand is a sunnah.
And concerning your question.. ive heard somwhere.. (I might be wrong, Allah knows best)
For example you've been eating a sandwich with your right hand and its kinda messy.. and you want a sip of your cofee or tea...