Here is the issue, back on october i took my Viola to a Luthier and he did the following changes:
-Fixed the button.
-New Strings (D'addario Zyex)
-Changed sound post position as apparently it was not on the optimal place.
After that the instrument was not the same as i used to play it was better by far! I loved how it sounded... Even my teacher was amazed by the sound.
Now it have been 2 months since that and i feel that the instrument sounds weird like it got a cold sound... not as warm as before... What could it be? the strings should still sound good... but i dont know, i hope i dont have to change them again...
What is the humidity level in your home? Some instruments are very sensitive to humidity changes. Dryness from having heat on or too much AC.... Humidity from lot's of rain....
Do you play as much now as you did when you got the viola back from the luthier? Did you ever drop the case with the instrument in it? Sound-post can have moved.
I found the issue... i feel like a noob... i have been practicing a lot lately and suddenly i stopped playing for like 2 weeks so i forgot to put more rosin into the bow... due to that it started to sound weird... after posting this i went and added rosin to the bow and now it sounds good again...