Bottom leaves dying, Deficiency?

I'm in my third week in bloom and my bottom leaves are starting to die, I have both my plants (Nirvana White Rhino, G13 Labs Purple Haze) in DWC which i fed them aprox. ( dont have a ppm meter) a little more than a tsp of each AN Grow, Micro, and Bloom and ph level is around 5.8-6.0. I didn't have this problem last week. This is my second grow (first time Hydro). Do i need more phosphorous?

its normal, just pluck em off. plant trying to get more oxygon to lower stem, they like that.