You're done with growth basically dude. At about the 21st day maybe that is about it for your plant. All the rest of the time will be bud development, so you have PLENTY of headroom in the system.

But on a more serious note, you way over grew your 400 watt. It can only penetrate like 2 feet or so and thats from the bulb. So everything you have below that is not going to grow.

For 400 watt you should veg to about 6 - 8 inches of height. Then it will flower to about two feet and you wil get some good results.