You can track the performance of themes by tracking the index value. When you make the investment, the index value is set to 100 by default. If the value of the index goes up, it will reflect in the index value too. Let’s say it goes up to 110. It means that the theme is up by 10%. You can also view the 1 month return & 1 year return in the snapshot of the theme.
If you want to view the historical performance of a theme, you can check plotted graph against Nifty Index and Gold which is available in the overview.