Check out my journal in my signature. The middle row back plant is an auto Jock Horror that has reached 31 inches. That will give you an idea of what you are looking at once those plants take off and if they reach their stated height. The middle front plant is a 25in tall Jock Horror.
I would personally get them separated before the roots become so entangled that you have to chop them apart since you already know they are females.
The reservoir I have is 27 gallons and I am concerned about the current 4 plants being over crowded. You might look into a couple 3-5gal buckets and 2 cheap air pumps to bubble the water since the roots should be long enough to reach the water easily.
At worst you will end up with something looking like my Blue Mystic but those plants already look like they will be larger then my blue mystic.
tho on the plants, they do look healthy and strong! Just wait until they start flowering!