Nice job on your grow...I wouldn't stress too much, it will probably be fine with some tweaking. I would start by checking the PH and EC of your water. From there you will know what your total PPM is of the water (I target between 1000 and 1300 depending on the stage), and this will give you a good idea of whether you should dump your resevoir and build a fresh mix of h20/nutes.. I would target for a PH of 5.8 or 5.9. You are right that it looks like a deficiency, but I suspect its likely due to your PH (especially if your water already has a high ppm). I would also pluck off the dead/burnt foliage at the base of your container. HTH!