Sounds like Corid is in order for sure - Silkies go down fast, they just don't have the resources of a LF juvenile. While Coccidiosis is not as common here as in areas with more humidity, it does exist. You did all the right things - warmth, giving her a chance to eat uninterrupted, and probiotics. After the course of Corid, if no one remains symptomatic, you will want to boost vitamins for a bit, as Corid blocks thiamine uptake and can affect the correct balance of B vitamins, which is thought to be a possible cause or contributor to wry neck, which Silkies are more prone to than other breeds in general. I didn't know that until I had one with wry neck last year. Luckily she fully recovered, and while in treatment in the bathroom was dubbed Peep Peep - she would peep at us anytime we went in to see her, the sweetest little sound