"showed decline" is correct and usable in written English.
You can use it to indicate that something decreased in size or value. For example, "The stock market showed a decline this month."
This positive impression of frontline staff bucked the trend, which showed decline in trust across a range of professions.
Results showed decline for all symptoms in the intervention group (linear trends ps<.05), whereas stress management skills remained stable.
Results: None of the patients showed decline in Subjective Global Assesment category, and 2 of the patients improved.
Afterward, both strains showed decline in chlorophyll a content to 8.59 and 8.88 mg/L, respectively, on the 12th day as microalgae cells entered death phase.
In the growth curve, drawn in laccase medium at an interval of 6 h up to 48 h of incubation, the maximum biomass was attained at 24 h that afterwards showed decline up to 48 h.
Pyruvic acid, an important molecule in the glycolytic pathway, showed decline in its levels in infested tissues at 48 hai in accordance with the up-regulation shown by the transcripts encoding pyruvate phosphate dikinase, an enzyme utilizing pyruvate as substrate.
