it looks as if you started this bluberry around the beginning of March.
Having racked from primary to secondary, usually you want to rack again within two to three weeks.
Doing that will delete what ever protective CO2 you have developed and leave you wine open to nasties.
You can add sterile marbles in any quantity to raise the volume and diminish the air above your wine or you can top off with some type of liquid (water, bluberry juice, grape juice etc) to accomplish the same thing.
Since I assume that youll eventually want to raise the sugar level by backsweetening at some time, now might be a good time to do that.
Adding sugar will increase your volue as well.
Youmight consider racking your wine to another carboy, sweetening and then leaving it to age several months in the carboy too.
Just food for thought.