1. Yes
2. I'd be very surprised if you actually found a Phosphorus deficiency in Cannabis.
Well.... two crops ado, my first run with cobs, I suspected it. But as a result of salt build up and lock out. 2nd run with the the cobs it happened again even though I was very careful to protect against it and watched ph like ahawk. Now on my third run with the cobs and by now I recognize the early stages of the same thing starting all over again.
The symptoms showing are exactly what I have read p deficiency to be (never had it before). Reddening of the stems, blue grey spots thatv started low and work up... and now... the new growth is light green with grey blue edges...
So I dunno....
Unless that happens from overwatering too I don't know what else it could be.
Doesn't surprise me though. These cob lights are great but the type of light has actually changed the physiology of the plant...