Is this leaf burn?

I remember my first indoor grow. I had been gardening for decades and decided to try my hand at an indoor cannabis grow. Using my own knowledge and experience led me to believe I could just ignore the PH of the water. Afterall, I've been growing outside forever and rainwater isn't PH adjusted, so what's the harm, I thought. Wow was I ever wrong. At some point I got a good quality PH pen and checked my tap water. Low and behold it wasn't even close. I made the appropriate adjustments to correct the PH and the plants took-off after that. Now I check it every watering, even if I adjusted the water yesterday and have leftover. Check your basic conditions, watering, etc. and keep it simple. Also, it helps if you know something about the strain you are growing. I'm partial to sativas and they like to be watered more often with less water than a lot of indicas and hybrids. With bag seed it's a bit of a crap shoot (even buying "good seeds" is a crap shoot somewhat.) Good luck with your grow.

I can add from experience, at least in the beginning using the Fox Farm trio, it's best to start at about half strength and see how the plant(s) handle it. Depending on your soil they don't usually need full strength right away. I would feed ever third watering, water water food, water water food, when I used FFT.