they have nute burn on the tips, i would also say the PH is way off, do you set it? read it? did ya soak the cubes in a 5.5 PH water b4 using them,

the thing is with hand watering rock wool is the longer it sita there the higher the ph and the more concentrated the nutes become due to the action of evapouration! i think an enzyme wash once a week at least to give them a chanc, lower and control your feeds and PH the sollutions to 5.5 until they come out about the same or 5.7, thats the water that drains out!
good liuck, ant get them in some arlita [hydroton] as soon as poss with an automated feeder,

welcome to the world of endless possibilities,,,,,hydroponics