I hate to go there, but.. as someone who previously bred Silkies.. I would consider and suggest switching to a more nutritious feed.. Purina flock raiser is a better choice for Silkies than that.. with higher
protein and
amino acid levels.. in addition to a LITTLE more fat and lower fiber content (means more digestible to me).
Plenty of chicks are raised on that feed.. and it may be fine for most of them. I
don't think your death is specifically related so I hesitate to mention it at all but I'm giving a personal opinion based on nutritional research, hatch results/analysis, and long term keeping of said specific breed which showed SOME individuals needed a little more help.
The amino acids really make a difference. (possibly the magic in Poultry Nutri Drench) Both links include the guaranteed analysis (product facts) for comparison between the feeds being discussed..
https://www.mannapro.com/poultry/chick-feed/chick-starter-grower-medicated
https://www.tractorsupply.com/tsc/product/purina-flock-raiser-crumbles-premium-poultry-feed-50-lb
Medicated feed uses LOW dose amprolium.. even though it is preventative.. outbreaks can still happen and need other treatment, most often Corid. Sometimes a sulfa drug. If using Corid (amprol) do NOT substitute with extra vitamin supplements as it works by mimicking thiamine (B1) to starve out and slow the growth of the coccidia. Droppings can be tested by a vet to confirm if coccidia load is high.. Doing the drench dose of Corid is safe even if coccidia load is not high or that wasn't it. Sometimes shavings look drier than they are.. keep shavings dry and change water every time it gets a poo in it as this is the fastest way that coccidia spread.. Just general discussion for good measure, not saying that's actually what happened.
The reason for my breed question is because some breeds carry lethal genes that may not kill them in vitro (or until slightly older).. Silkies are not in that category.
I definitely would NOT exhume the chick, (now I see it happened a few days ago, there are unlikely any viable result to be had) but consider refrigerating if it happens to another while deciding what to do.
Regarding grit.. Most starter feeds don't require grit to be fed, but it does help with gizzard development and
perhaps if anything else is accidentally swallowed. One of my favorite ways to provide it (after any vaccine quarantine time is passed) is by bringing in a dish or clump of grass.. dirt, bugs, and all.. from the space where the chicks will be going once ready.. it gives them natural grit, enrichment playing king of the mountain, as well as LITTLE exposure (to help build immunity) to the things in the ground before going out on it full time. I use commercial packaged grit products if given during quarantine.
The only other possibilities I've seen but consider uncommon at this age would be.. pasty butt (pretty well fits your description, do you know if it was clear) and drowning via accidental inhalation of water most often from being dunked upon arrival (and the lethargy set in immediately) but maybe bumped later.. usually crackling sounds during breathing is also quite obvious.
How many more chicks have ya got? Any signs of sneezing or wheezing, coughing, or other unexplained sound? Everyone running around, energetic, eating, and drinking? I probably wouldn't treat even with Corid without cause (due to resistance being a factual problem).. but rather be on the look out for anyone slowing down or starting to show symptoms and then be ready with quick assessment/response.
Please note that this statement taken from the mannapro link is inaccurate, as birds WILL still continue to build immunity against coccidia, just with additional support to their keepers husbandry practice! Using amprolium does NOT prevent or decrease immunity.. Now I know why this question was asked recently! My guess the word "not" would have to be a misprint???
"ACTIVE DRUG INGREDIENTS
For prevention of coccidiosis where immunity to coccidiosis is not desired.
"
Have they been outside and in contact with the ground? Have other birds been maintained on these grounds? At 3/4 weeks of age it is unlikely that they have a significant gapeworm infestation. Respiratory disease seems more likely.
