Sorry im an idiot, was tired late last night an i posted the size of the flower room not the flower space (space taken up by pots):

Really the space will be: 6.6 x 6.6 ft = 39.6 sq.ft

so having 27 plants = 39.6 divided by 27 = 1.46 sq. ft each plant.

Lumens per square foot:
1x 600w = 90,000 lumens so 2x 600w = 180,000 lumens
180,000 divided by 39.6 sq.ft = 4545 lumens