OMG! They are so cute!!!
I love your gerbils, they remind me so much of my RB gerbils Chocolate and Brownie.
You did a good job getting photos of all 3 of them and a video too.
It is so hard to take good photos of black gerbils because they are so dark and gerbils are so hyper in general.
You will have so much fun with them.
I did the same thing that you do to tell them apart, by looking at the amount of white on their paws.
Of course when they are all curled up together sleeping it will be hard to tell them apart but their unique personalities will help keep you from getting them confused most of the time.
Congratulations on your cute new additions and let me know if I can help you with any gerbil info.