That is definitely nutrient burn. You need to flush the pots out until the excess water runs clear. A lot of water! When they stop drooping, re water with just water for a few days and go back to a very light water/nute mix.
Looks like the same thing home depot has for $4 ;)
http://www.homedepot.com/h_d1/N-5yc1vZ1xh8/R-100685881/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053