Your feed may certainly be part of the problem. If you are using a grain mix feed rather than a pellet or crumble, there are a number of serious concerns about them, especially if feeding them adlib. As you mention, the powdery fines which tend to contain the minerals like calcium and essential amino acids are often left in the bottom of the feeder and if they have the opportunity, some birds will pick out their favourite components, usually the high carbohydrate grains and leave the healthier protein rich pulses which causes them a dietary imbalance over time that can lead to them becoming obese and suffering reproductive problems like egg binding or prolapse and/or salpingitis and even internal laying. Fat particles can also build up in the liver and cause Fatty Liver Haemorrhagic Syndrome, which can cause a massive rupture of the liver and sudden death in a seemingly healthy bird. Heavier birds like Orpingtons and Sussex are more susceptible to Fatty Liver Disease.both feet are out the front, not splits. I have just given her 1/4 tablet Uncrushed (it’s night so I’ll crush some in breakfast) think I need to adjust my flocks eating habits as they don’t eat the fine grains in the bottom of the feeder. Probably where the good stuff is. Brew shop tomorrow for some yeast. I have a pigeon problem in my run, so spread of Maleks is inevitable. She is from a reputable breeder, so surely vacced.She’s still only year + 1/2 old. I got new girls 6 months ago.
I would also be surprised if your reputable breeder vaccinates for Marek's. The logistics of it make it difficult for a small scale producer because the vaccine only comes in 1000 dose quantity which needs to be kept chilled and once the active ingredients are mixed it has to be used within an hour. Added to that, you have to operate very strict biosecurity of the chicks for several weeks after vaccination, so for someone who isn't hatching hundreds or thousands at a time and isn't set up for it, the cost and effort is not really feasible. The vaccine that is available is also problematic because it does not prevent the birds from getting the disease, but should protect them from the most serious symptoms, so vaccinated birds can be silent carriers and the virus has the opportunity to mutate inside them because it doesn't kill it's host. There is a school of thought that the more aggressive strains of Marek's which are becoming more prevalent are due to this vaccine allowing this mutation.
I would not bother with the brewers yeast if you are giving a human Vitamin B complex to the bird as that is what the yeast provides. Whilst vitamin B is water soluble and excess can be excreted, it is not a good idea to overdose, even on vitamins.
