i had a simliar thing happen to my plants and im pretty postivie it was Mg deficiency. i took Blazins' advice that i saw on another post and treated with epsom salts. This was 2 days ago and my plants are showing some recovery signs.
i have also had an issue like this with my soil plants, and pH was the simple issue. i flushed with pHed water and tested the run off.
I do not know about Stealth hydro. but i do know that with my system, the aerogarden, it comes with nute tablets.
on other posts ive read that the nutes are wayy to hot and damage the plants. You may want to look into what nutes you are using- if they are for specific plants, like peppers, salad green etc, the nutes probably arent what you are looking for.
you say they are "packets" so it doesnt sound like liquid. if you continue with those nutes you may need to decrease the strength and that may avoid any more burning.
FoxFarm is all over this site with good results. They sell a 3 part hydroponic nute kit. Remember to dilute properly (i.e 1/4 recommended stength to start out). For my aerogarden i am using Advanced Nutrients : Vitaboost Pro, and Iguana Juice