The "no lemon" doesn't seem surprising to me. Many/most lemon concentrates are fast faders. And, with your mix being nearly 2 months old, I would expect the lemon to be gone. You could try re-adding the lemon components to the mix (or portion of the mix) and see if that perks it up.
Lemon Sicily, in particular, only has an identifiable presence, for no more than 2 weeks (to my palate).
If I am mixing a recipe, that uses ingredients that will require a long time to develop, I will leave the lemon(s) out of it until I am only a week away from mixing (if that long). Otherwise, by the time the rest of the ingredients have come into their own, the lemon has left the show.