You have done a lot with a small space and setup. Looks like you have mastered grow room management. 1/4 pound isn't a lifetime supply, but it is a good yield for 400 Watts. You mentioned adding more lights, and having just switched from 400W HID lamps to LEDs, I strongly encourage you to look at that option before you spend more on a larger and hotter discharge fixture. Were it me, I would consider spending your dollars on a couple small LED panels to supplement the 400W fixture you already have. The 'wide spectrum' LEDs should get along with that in both veg and flower phases, and they run MUCH cooler in a closed space. Having the option to move a few light sources around your grow space also makes it easier to accommodate your plants as they grow and need to be re-arranged.