Looks like Phosphorus deficiency to me. What kind of soil are you gonna use for the rest of the grow? The seed starter mixes dont have alot of nutrients in them so they are usually only good for a week, two weeks max. Do you know the ph of the ingoing water you are using? Im willing to bet that if you transplant into some good soil and have the ingoing water around 6.5 ph. You will be good to go. The burnt looking leaves will not recover but the plant will continue to produce more. Another thing that will help you out is to use the whole pot/cup. Fill them almost to the very top. Leave a little lip so when you water it stays in the container instead of running on the floor. You have holes in the bottom of those cups right? What kind of light are you using? What are the temps in that area? Air circulation?