Reloading with out a chronograph is like driving a vehicle without any gauges that work. You might still get where you're wanting to go, but having that info at your fingertips might help you avoid a speeding ticket, an overheated engine, loss of oil, well you get the picture.
You can get a decent chronograph like the Chrony for less than $100.

Velocity alone is not an indication of pressure, but looking at the chronograph readout can tell you how consistent a load is, how fast a small increase in powder is affecting velocity, and when you should stop increasing a charge, instead of just the round "feels" when fired.

I'm not saying your loads are for sure underpowered or you should bump them up. Just one of the many possibilities.

One thing I do, to every pistol round I load, is to try each one in a Wilson or Clymer gauge. I have a gauge for each caliber I load for. If it doesn't drop in and out of the gauge, it's not going to work well in the pistol. You can do the same by removing your barrel and trying each round in it using the "plunk test".
Weird that you've fired 500 rounds of your loads without issue. Maybe something you did differently this time ?
L.E. Wilson Max Cartridge Ga 9mm Luger - MPN: PMG-9MM