I have 'adjusted' several Hybrid Kydex/Leather holsters over the Years.
If a holster is truly Kydex (as opposed to Injection molded plastic),it can be adjusted with the application of Moderate heat from a Hair Dryer (and oven mitts).
Normally, the main areas of adjustment are the barrel (obviously), especially around the ejection port (which serves as one point of minor retention) and the trigger guard (a primary area of retention).
There are many YouTube videos showing the technique needed.