Truly need help had my purps for 4 yrs cloned and just hit a wall

Ok so all my last grows have been great and this time around there in need of help and I can't figure it out pale green some what red stem I thought N but I just can't shake it I had a fungus gnat prob from the soil I got and that's almost taken care of if any one could help I'd be most great full ill send pics if needed there clones if that has any thing to do with it plz save the purps

much more info needed. How old are they, what medium are you growing in, pictures would be nice.
I did have a similar problem, turned out to be root rot. Check the roots if you can.