One of the interesting side effects of addressing a dysfunctional microbiome was the major reduction (almost disappearance) of my prior psoriasis. This makes sense because the level of inflammatory chemicals in the body would drop which would affect all aspects of the body.
Of course the question arises — is there any PubMed studies that could back this observation?
” recent research has identified a group of conditions probably resulting from dysbiosis, or alternatively referred to as originating from a misrecognition or aberrant response to the normal microbiota, including inflammatory bowel disease (IBD), psoriasis (PS), bacterial vaginosis (BV) and periodontal diseases (PD) (23–26). These four diseases seem to cluster together from an epidemiological, pathogenic, genetic and microbial standpoint, with similarities between them being recently reported (27–36).” 
This article goes on with:
Over 50 years ago, it was noted that two thirds of patients with the variant guttate psoriasis (GP) had a preceding sore throat and serological evidence of a streptococcal infection (59). This was then confirmed by the isolation of beta haemolytic streptococci [BHS] from the throats of patients with GP (60). Furthermore, guttate flares in chronic plaque PS are associated with streptococcal pharyngitis (61). Microbiological analysis of psoriatic skin report conflicting evidence on types of bacteria associated with the lesions: 16S rRNA gene analysis using swabbing of the skin to recover bacteria, has revealed differences in bacterial colonisation compared to healthy skin, with an increase in Firmicutes and a decrease in Actinobacteria.”
Another article  states “we hypothesize that common immune-mediated inflammatory pathways seen in the “skin-joint-gut axis” in psoriatic arthritis are induced or at least mediated by the microbiome“
Now for actual on human studies with patients with psoriasis :
“In conclusion, oral administration of a single microbial agent, B. infantis 35624, was sufficient to reduce systemic inflammatory biomarkers in both gastrointestinal and extra-intestinal inflammatory disorders. ” This study included 26 patients with psoriasis. This probiotic (commonly sold as Align) happens to be one of those that I took.
Conclusion: my improvement is psoriasis was indeeddue to the probiotics!