Q: Cylinders misfire after using motor flush and oil change - possible sludge issue?

I was due for an oil change, so beforehand I used Motor Medic Motor Flush in the crankcase and let the car idle for 5 minutes. During this time, the engine sounded great. The longer it ran, the lower the RPM would get while idling and the better the engine sounded. I drained the oil & motor flush then proceeded with a normal oil change. I also added a can of engine restorer in the crankcase with the new oil. When I first turned the car over after the oil change, it sounded great. Then after the car ran for about a minute, the car started shaking more and more and the RPM got a little wonky. Going up and down 200 RPM each way while idling. I shut the engine off immediately and haven't turned it on since. I took it to the shop and they found that all 4 cylinders are misfiring. I think the motor flush knocked some deposits and buildup loose and that is what's causing the issue with the cylinders, but I'm not a mechanic. What would be the best (cheapest) course of action next?

This is a 2001 Toyota Corolla. My car has 148000 miles.
My car has an automatic transmission.