Without expressing an opinion on the merits of your case, I would answer the specific question asked by saying it is the common practice among attorneys to name as defendants any and all persons, companies, etc. who/which might be in some way responsible for the harm complained of in the lawsuit. It is easier and cheaper in the long run. Let the defendants fight it out between themselves as to which is responsible. One overall caveat is that you must have some reasonable basis for believing a party might be liable to you before dragging them into a lawsuit; otherwise it could be malicious prosecution or abuse of process.
