400w hps Is it enough...

So Iv got a small indoor space of about 4ft x 5ft (6ft tall) with a 400w hps and in there Iv got 4 sour diesel, 3 northern lights and 2 super crystal. they are about to go into flowering, because i just took clones from them, and i was thinking that i should get an extra 200w hps or upgrade to a 600w hps which do y'all think would be the best option ? + is their any other way i could get more light with out getting too much extra heat ?

400watts should be ok for 9 plant i have 24 aks all lollypopped under a 400 watter

Get more light.
400/ (4x5) = 20wpsf
General rule of thumb is a minimum of 50wpsf

I would say 9 plants is ok but the 4x5 area is too big. I would say pack the 9 close together in a smaller space. so you can get more light/ sq foot. Like hang a curtain of mylar up or something. & then make sure you don't get your 9 too big. A scrog would prolly work well on 9 plants in a 3'x3' area. veg them just enough to fill up a 3v3 screen & then go to budding.