It seems that vets cost a lot...and lots of vets don't work on chickens. That being said when you actually need a good vet there is nothing that can replace their skills.... In this case however.............
Most people worm their own chickens.
If you have chicks, and they are growing...
seems like you wouldn't have quite the climate we have here---but have you considered treating your chickens for worms?
Lots of folks worm on a regular schedule - spring and fall. --- It could be one thing for you to consider.