Agree. Check the plugs. Coils fire 1&4 and 2&3. Your coils must be working as your getting spark out of each coil. I’d look at fuel supply to carbs 1&2. There is a tee between the carb bodies. It supplies fuel to the carbs from the petcock. Check the petcock to make sure you have flow out of both nipples. When the engine is cold, you can put rags under the carbs and open the bowl drain screws to check for fuel. Also check the vents on the carbs. It the vet is plugged it could restrict fuel. See red arrow on screen shot for vent.
Looks like 1&2 and not firing. 3 is either rich or just sooty because it was just run at idle. 4 is good see the color change on the ground strap it starts to get dark at the bend. That’s what you all of them to look. Still need to figure out why 1&2 are not firing. Also Slmjim brings put a great point. Make sure you service the brakes before it leaves the yard... You can try a quick shot of starting fluid into carb throat 1&2 to see if they will fire.