Gotta get this sorted out!

I can see down into one of them and it seems to show a decent wot af, but the rest is rich and fouling and when they foul ...they don't fire or very well and you will lose rpm like you did. I think there is a chance that you are not in the idle circuit, I don't believe you should need 1 1/8 turns out on the 4 idle screws, but hey... Get new plugs 1st, raise the initial timing to 25 or so, set the idle screws at 3/4-7/8 each.....and let it sit and idle. Check the plugs around the base for dark color but no soft soot, you don't want soot.
Give all the carb specs, jetting, PV, shooter size. You probably needed more initial to keep the carbs throttle blade square with the transfer slot....you night be idling on the mains and that will foul plugs.
Now again....if you aren't leaning the primary jets down and just running it as is...not only might you be in the main circuit while idling...but also just re fouling the plugs also by too much jet.
now I don't see soot on all the plugs, but you could have a fuel distrubution issue In the intake or ring/valve sealing problems.
I would be getting the idle position fixed first before driving it...then I would be leaning those jets and seeing the plugs clean up.


After all this....I hope you have good spark, check it and see if its orange colored...that means you have a problem with too lil spark energy, ignition issue still.