Purple stem? Phosphorus deficiency? Picture included.

[1st timer]

Hello

So the stems which lead to single but large leaves (fan leaves i think theyre called) are purple on one of my plants. The stems off the main stem which branch into a few leaves (colas i think they're called) are normal green.

I read this could be a phosphorus deficiency, but the last two feeds i have given them bio bizz bio grow and they have a decent bit of bat guano mixed in the soil.

Thoughts please?

[1st timer]

pictures here:

[1st timer]

and to hi-jack my own thread, some help on lighting please.

background-
they are now vegging 24/0. they have 15 hours of natural sunlight and 9 hours of CFL 2700k (flowering) 250W.
I will soon move them into flowering, wholly on the 2700k for 12 hours and no natural sunlight.

i was previously hanging it vertical in the middle of the plants, until today, because the plants are getting too big and the space is limited. I now have a reflector hood and keep it above the plants. you can see only two of the plants are getting proper light.

question-
a)should i get another cfl to top up? (3 plants, 1x250w doesn't look like it's enough to flower)
b)i have a flowering cfl now and only have money for one more bulb- should i buy a purple or a blue? i have been vegging them on a 2700k (red, flower). should the next bulb be a blue (vegging) cfl, or should i use my money to get a purple which supports flower and veg i believe. the plants look like they will need more light during flowering, but during veg they were ok on just the red (flower) cfl.

i'm hoping to get a 125W, which isn't so large and can fit between my plants, vertically, as a top up to the horizontal 250W.

please share your thoughts! i am looking forward to your opinions :)

[lipps]

Some plants have natural purple color so look at the over all health of the plant and if the others are not doing it it's probably genetic.