Accelerate can be both a transitive and an intransitive verb.
Passives are formed from the transitive.
Adding fuel accelerated the fire. (active)
The fire was accelerated by adding fuel. (passive)
The fire was accelerated. [by something which is not mentioned] (passive)
The race car accelerated through the banked turn.
If, in your example sentence, you say were accelerated (passive) you are implying that certain (unnamed) factors accelerated those processes.
If you say accelerated, you are saying that they gained speed but your sentence is silent with respect to the cause or the causes.
Complicating the matter is the fact that past participles of the verb can act adjectivally. It is possible to understand the word accelerated adjectivally, with the meaning "possessing the characteristics of that which has been caused to progress with increasing speed, or of that which progresses with increasing speed". At the core of that idea is the possibility that there was a cause of the increasing speed; but inasmuch as the word is being parsed (understood) adjectivally, the question of whether the verb phrase is active or passive is mooted. In this parsing, accelerated is a predicate adjective modifying the subject.
So, if you wish merely to point out the increased rate of speed, without reference to the cause or causes, you can use ...accelerated. or ... were accelerated.. If you wish to point out the causes: "... were accelerated by factor X and factor Y".