You mention putting the digestive enzymes on food at a certain dose, but do not say how to administer the drops ( at .25 ml). If on food, see below. If directly into the beak, see below.
It seems your Lucy kept eating, and probably also was not showing the profound lethargy -- mostly sitting, and a wide, slow (something in abdominal cavity?) gait when she does walk -- I am seeing with Ev. These additional symptoms would align with an underlying problem. I did not see them in the only other hen I've treated (miconazole/ACS water) for sour crop; she fully recovered and lived several more years.
Ev is nauseated and not eating. That is the reason for not trying, as I would have to force her, which I don't want to do when my vet expresses no doubt she is terminal. (I did actually mention your idea to her.) If you can help me get around that, I'm all ears.
I hope your Lucy stays well and gets to be at least 6, my girl's age. Unfortunately, we both understand that this kind of issue is apt to recur -- especially with older hens -- if there is an underlying problem. I hope that's not the case with Lucy.