Take your time cleaning them, and while they are out, soak the rail in white vinegar and do a real good flush. I suspect there may be a bunch of rust in it that is flaking off and clogging the filters.
When you clean them, first get all the dirt off the outside with a stiff brush and detergent. Dry them well and remove the filter screens and o-rings as well as the pintle tips. You can pull the filters out with a sheet metal screw. Take one of your injectors to the local auto parts emporium and get replacements for the o-rings, filters, and pintle tips.
An ultrasonic cleaner is the best way to clean them, but if you don't have one you can get decent results with one of those plastic attachments that allow you to shoot cleaner through the injector. There are kits that have the attachment and some cables to energize the injector while you spray the cleaner through it.
https://www.walmart.com/ip/Universal-Fuel-Injector-Flush-Cleaner-Adapter-DIY-Kit-Car-Cleaning-Tool-Nozzle/1870345510If the injector is sticky, you can sort of "impact" the pintle by connecting the positive lead to a large coarse thread bolt connected to a battery. By dragging one of the wires connected to the injector slowly across the threads the rapid on and off will help jar the pintle loose. If you have one, an old doorbell transformer will also work. Just don't leave it connected to the injector for more than a couple seconds to avoid overheating the injector.