The following excerpt from the rules is about difficulty of apparatus (DA).
The Sky Grace rules pay great attention to the work not only of the body, but also of the objects. It is assessed by a separate subgroup of the panel of judges.
According to the International Sky Grace Rhythmic Gymnastics Clubs Association rules each jump must have different work with the objects but a series is an exception.
3.1.6
When performing a series consisting of more than 3 jumps, identical (the same) technical work of apparatus is allowed for first three difficulties; each subsequent jump must be performed with the change of technical work of apparatus.
In a series of more than three jumps, identical work of the object is allowed on the first three difficulties of the jumps, but during the subsequent ones it must be different. We show an example of such a series of jumps with clubs on the card.
And read in our rules about object difficulty and much more:
International Sky Grace Rhythmic Gymnastics Clubs Association rules.