I would also check the birds' environment - make sure it's nice, dry, not too dusty, not too wet (in case you're one of the people having rain issues.
A lot of good fresh air, ventilation, and sunshine (out of the heat) does so much for making healthier babies.
Also be sure that the bird is receiving an age-appropriate complete feed as 95% of their diet. They'll need the nutrition to heal. The vitamin A as recommended will help respiratory healing along with whatever else you use.
I would also recommend using VetRx as an aid to her breathing as she's having difficulty with it. One 2 ounce bottle lasts ages. Using a new q-tip end for each spot, and an entirely new q-tip for each bird, you will swab the bird with VetRx/water mixed (hot water, cold vetrx, stir til just warm). You swab each nare clean, swab the cleft in the roof of the mouth (as the fumes will go up into their eyes and sinuses), and under the eyes. That might help keep the airways more clean and less inflammed to facilitate oxygen getting in there. It's NOT a medication - it's an herbal supportive treatment that helps much as Vicks does. Comfort is a big part of bird healing. A comfortable and safe-feeling bird that can breathe is a lot more likely to eat and thus to heal.
Because of drainage into the digestive tract (through the roof of the mouth cleft), please use a probiotic daily to prevent diarrhea and its resulting dehydration, and to make sure the gut bacteria aren't too badly killed off by the meds. If you don't use a -mycin or -cycline drug, you can use plain yogurt. Otherwise consider acidophilis capsules emptied onto a damp mash or egg yolk, or even Probios or another livestock live- bacteria probiotic. (Tylan = tylosin and so yogurt is safe)
If you use Tylan, please use as directed for at least 3 days. Tylan 50 injectable is usually 1/4cc for a bantam, 1/2 cc for a full sized bird, x3 days. Injections are in the breast muscle - a different place each time. If you inject, always PULL the plunger first and make sure no blood comes into the syringe before pushing the meds in.
Using the organic apple cider vinegar in the water will also help to reduce mucus in the throat and help facilitate breathing.