Help, red stems and stunted growth, DWC

hey guys, this is my first dwc grow, i've been searching the internet trying to pin point my problem but nothing seems to fix. I have two 3.5 gallon 4banger bubble boy units, with 3 plants in one (strain: Heavy Buds), and 4(strain : THC Bomb) in the other all grown from seeds.(i know one of the 4 will have to go come flowering but i wanted to make sure they all made it since it's my first grow) They are on Floraseries drain to waste feeding schedule, and are in week 5 of veg. They have been showing signs of stunted growth and purpling or redish branches and in the nodes, as well as yellowing and dead spots on fan leaves. it seems to be spreading to the main stems (i topped them) and their growth has stunted. Also on of the plants has curled up and pretty much kicked the bucket, however the one thats dying is part of a double sprouted seed. I've got a ph of 5.8 and not sure of the ppm. Ive read it could be phosphorus def, but before they red spread, they appeared to be showing a cal mag def. but it i def affecting both strainsmaybe somebody can diagnose and suggest treatment for the babies?

One time I would advise you on (K) def, but is so prevalent with these modern strains its just to difficult to say, for now I ignore the red, but the rest of the grow has symptoms typical of accumulated nutes, flush ...flush again and re feed at 50% of what you have been feeding at, at least for the next 2 weeks, ...you must be going to budd soon and a change in nute feeds to ...? so again caution with the feeding, keep an eye on your night time temps may help the red stems ..good luck

thanks for the response. ill keep an eye on the temps and flush flush flush!

What are you using for pathogen control?

Thanks Buds ...I missed that Ugh!!!! the cow ! should read this on Neem Oil for bugs and Molds ....https://www.rollitup.org/blogs/blog32238-neem-oil.html

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i am using Aquashield, thats all