The first sign of any problems always best to flush the plant with water ph of 5.0/5.5.If you have been growing for a while then you should have already have done this.But if you aint then do it bro don't just think that flushing plants is just for the last week or two.Get into the habbit of flushing has regular has possible,Some might say that by flushing the plants you are takeing away the nutrients to beat this have a fresh batch made so once the flush is finished a couple of hours later make up some fresh and put them in with the plants.Best to do this over the bath because alot of water is about.But i flush at least 3 times during veg and once aweek during flowering a little extra work but if you are watering right you can time the flush with the feed.Only feed once a week there is no need for any more wet the plant through and repeat on the same day a week later after you have flushed the plants.If you are growing loads of plants then this would be realy hard work but i grow 4 plants and get about 3/4 ounce dry of each.