T-5 to HPS during flowering, Questions???

I just borrowed my buddies 400 watt hps and set it up for the last 2 weeks of flowering for my bubba kush. Should I expect to see any difference visually? Will it make very much of a difference? Do you think this was worth the effort? Here are my specs:

2 months veg...9 weeks of flowering on this:
( T-5's @ 351 watts 32,700 Lumens= 5,400 Lumens per sq ft

Last 2 weeks:
(1) 400 HPS 48,000 Lumens = 12,000 Lumens per sq ft (fyi smaller grow room)

you'll see a nice lil difference, prolly'll get less whispy and more dense. even if its the last 2 weeks, id say its worth it - although the difference will be little but still visible id say.

I think the whispy buds have alot to do with the strain. I grew sensi in the same setup and i got very wispy buds, but the bubba is SOOO dense! So i am very excited to see any difference!

Another Question: I know I am 2 weeks aways, but would it be worth it to add some nutes for week one and then do 2 flushes in the last week? Or should I just flush it and leave it alone?

anymore suggestions?

damn well if its 1 or 2 plants under that 400 watt...its perfect..1 plant is even better cuz all the light is focused on that plant