Spark plugs

I left my car in the garage for inspection, after 1 week the mechanical guy told me that he discovered fuel injector seals in bad condition so he replaced them with new ones, also he checked the spark plugs of the engine and he changed just 1 burned spark plug leaving the other old ones.

I told him I will take the car for a while until I get quotation for the full inspection...
but "once I switch on the car I felt like it was shaking more than it used to be specially on stop or low speeds. (The sound was for every 1 or 2 second interval I was feeling the shake harder) and the exhaust was jumping with the sound too...

So is this problem came by replacing just 1 spark plug while leaving the others or he installed bad spark plug that is not suitable for the engine?

Thanks