Tips are turning colors, looked burned.

So my SFV is in veg state and I'm noticing that only the ones in hydroton look like this. The tips are beginning to yellow. I water 4 times a day. 6:20-6:40 pm , 12:20-12:40 am, 4:20-4:40 am, 10:20-10:40 am . Lights on at 6 pm and off at 12 pm. I have a 20 gallon resivoir, for nutrients I use, CNS17 Grow 200 ml and 50ml of mad farmer silica. Anything helps

Looks like Calcium but it's hard to judge in that yellowish light which really should be blueish light. Cal Mag Plus is great but she's a little sensitive to N so you might choose CaMg+ it's a great ratio of 5:1 also. Back to the the lights you need to run a higher kelvin with that plant it is starting to stretch out.

Edit: My judgement on sensitive to N is on strain not on photo.