A). Check your mechanics. These are top priority IMO. Look up Brent Porciou's mechanical analysises on YouTube if you must to learn proper mechanics. This will give you move Velo, and improve arm health. You may lose some accuracy, but it will come back.
B) Strength & mobility. Gain strength and mobility, obviously. Healthy eating doesn't hurt, either.
Really work on explosive exercises, especially for muscles like the calves (feel free to inform me on any you find.. lol :P) Your core and legs are the best at producing power, hit them hard. Remember to do upper body still, as it can't fall behind. Another thing that helps, work your decelerators. Yes, it can increase Velo. Your body can only go as fast as it can slow down, if you only work accelerators (i.e. Chest, triceps) you'll find yourself hurt, and having less Velo. Plyometrics/Olympic lifts are very helpful. I'm assuming you knew all of this, but there's nothing else I can say considering the details five.
C) Rememver there's no one fix that will raise your Velo. It takes dedication and hard work to do so, just keep working.