Question about lights

Hello, this is my 3rd grow but first in a few years last 2 went well. Growing 2 fem white rhino in an Nft tank with ionic nutes just cuz they were so easy to use in my last two grows. Growing in a grow tent an like the last two times i'm using a 250w hps plants are tied down and just into flowering gonna flush 1 week in an change to bloom nutes, not sure whether to go straight to full strength as so far they could barely hack half strength grow nutes with small signs of nute burn. Anyway i have a 400w hps an think i may use it this time, should i expect a great difference in yield as i've always made sure by tying down that the plants aren't that big so the 250w hps has been decent enough between 5 to 7 oz per plant. How far should i keep the light from the plants if i change as with my 250w it is less than a foot away and also wat range has a 400w hps got for effective intensity for budding?

get the light as close as possible without burning the tops (prob within 9-10"). my 250hps can be within 6" with good ventilation, obvi u should yield more with a 400 as opposed to a 250...

use your hand as a temp guide placed at the top of your plants. you can lower the light as far you can while keeping your hand comfortable.

Here a couple of lighting charts to use as a "guide".
One is for HPS and the other one is for MH.