The truth is that pH 5.9 provides little Mo, Ca, Mg, P, N...
Try raising the pH to 6.5 and see how they respond. Also, check the relative humidity levels in the grow; during the vegetative stage, it needs about 60/70% relative humidity!
In the end, they look nice, try the pH adjustment, I think it will work well for you, with that you won't need to load the plant with nuts.