If you are having to treat your MG positive flock monthly with Tylan, then you may want to switch to Tiamulin (Denagard) for 3 days each month instead.Nutri-drench for 2 days in a row.
I would normally agree about not using antibiotics but I am using them monthly at this point to treat MG and MD symptoms so….. lol
There are numerous threads here on BYC about using it as a maintenance for MG positive flocks.
Antibiotics are not going to help MD symptoms. MD is a viral, so unless there's secondary bacterial infection, then antibiotics are not going to make much difference.
Of course, keeping your flock closed - no more new birds coming in or hatching birds (MG is transmitted through to the embryo) and letting them live out their lives and die off is also a good option. Once they are all gone, then clean with Virkon S, let the property and housing sit for 3 months then repopulate from a reputable hatchery is a good practice as well.
I think all that has been discussed before too - so maybe not to even re-hash it.
Poultry Nutri-Drench is good stuff for quick uptake in little chicks or as a quick boost to an ailing hen, but imho (and look at the label!) it does not contain enough E to be used for treatment of a neurological symptom like you describe. Give the Vitamin E and B-Complex directly with some egg and her normal feed. See if she improves over the course of a week.