more lights

I have 4 females a couple weeks into flowering with a 400W HPS light on them. They are pushing 2 feet tall and I wondering if what I have will provide enough light through their life or if I need to add more for the lower part of the plant.

I've been considering adding some CFLs on the side, how much heat will that add?

Do I have enough light as it is?

400w is enough for plants your size. I have a 600w and can grow 10 plants up to about 6 foot tall in full maturity.

Having some cfl's for side lighting wont cause any harm but are not necessary, its good to get some light under the canopy and the heat produced from CFL's is minimal.