I use the same custom script to generate images from the same position, one time with the SentinelHub playground, one other with the WMS API, and I do not get the same result.
When I use it in an API call, I do not get the same result (black image) : http://services.sentinel-hub.com/ogc/wms/?SERVICE=WMS&REQUEST=GetMap&SHOWLOGO=false&VERSION=1.3.0&CRS=EPSG:4326&temporal=true&LAYERS=TRUE_COLOR&MAXCC=100&WIDTH=512&HEIGHT=512&FORMAT=image/jpeg&BBOX=10.0688437282933,78.4056837282933,10.1498562717067,78.4866962717067&TIME=2019-06-30&EVALSCRIPTURL=https%3A%2F%2Fraw.githubusercontent.com%2Fsentinel-hub%2Fcustom-scripts%2Fmaster%2Fsentinel-2%2Fndvi_anomaly_detection%2Fndvi_anomaly_detection_script.js
The period of processing is defined with TIME parameter in the call.
TIME parameter should be constructed as “FROM/TO”. If you only pass one parameter, e.g. TIME=2019-06-30, we truncate it to “TO-6 months/TO”.
So to get older imagery you should use TIME=2018-01-01/2019-06-30