I've been using Kalmbach maintenance feed with mine cause I feed my hens and drakes together with Oyster shell flakes or crushed eggshells in a dish to the side for them to take from when they need it. I haven't yet done this in the peak laying season though as my year old layers I purchased...
Oh wow that is expensive for a vet... We only have one we've found that sees ducks, 45mins away and was around $120 for the first visit. We bring our dog to a vet not far from there cause our local vets prices are crazy and they try to upsell you on stuff you don't need when you've made it clear...