Hi again,
I would suggest either of these, and both are okay.
Thank you for the beautiful flowers and sympathy card. Your thoughtfulness and kind words are of great comfort to me. "
Thank you for the beautiful flowers and sympathy card. Your thoughtfulness and kind words were of great comfort to me.
The first if you still feel good when you think of their kindness, the second if you want to emphasize how meaningful it was to you then. However, I promise that no one will criticize you either way.