Its hard to tell how yellow they really are with the HPS lighting, but remember that some plants may start to yellow towards the end of their life cycle, as they are consuming their last remaining energy to put toward bud production. At 5 weeks they are on the downslide of their flowering life cycle and may be using stored nutrients before you harvest. But with your high pH nutrients could be getting locked out. I don't grow in soil so I am not of much more help. Good luck! :thumbsup: