Yes, of corse, flushing takes out almost all of the nutes you added to the soil, but in 3-6 days after flushing you can start using nutes again without the worry of any deficiency.
i assume your using clones if ur only doin a 8 week veg. but everything seems like it should work. only thing i might suggest is if your using a 8x10x8 is more watts.. like if u havent already bought your 2 400's i would go with 2 600's
yo I got a 1000w hortilux in the space with 3 plants and a few lollipops. use 3 larger pots and train them to fill the space it will only take a couple extra veg weeks and you'll save seeds