Got some brown dry spots. Boron deficiency?

[Illyisanoob]

Ok I'm on my 3rd grow and I think I've come a long way. I've dealt with spidermites, overwatering, under watering, insufficient ventilation. But this one is new to me and I'm trying to nip this in the BUD quick as possible... Get it, bud. So I'm in the 25th day of veg I'm using fox farm of and happy frog mix 50/50 medium. I'm using soul synthetics player pack nutes. I'm using water I allow to sit in a 10 gallon tank with bubbles. I have some brown spotting in some areas of my plants. It's not all over but has spread a bit since I first saw it a week ago. I'm growing peppermint kush and la woman. The la woman looks o be fine but a cpl of the pep k plants are having symptoms. My ph is at 7.4 so I just flushed the plants with just water and a teaspoon of fresh squeezed lemon juice to drop the ph. If anyone has had this issue please let me know what I should do here. I'll upload some pics.

 

[Illyisanoob]

 

[Illyisanoob]

 

[Illyisanoob]

 

[BuddroGreen]

6.5 pH on soil when using liquid nutrients. Are you using a cal-mag supplement with the LED?

LED make the plant use or want a lot more cal-mag in the medium, even in soil.

 

[Illyisanoob]

I thought of that but wanted to get a more experienced person to have a look. Im going to grab some today. No I havnt used any cal mag. Thank you! Oh I forgot to add I was using 700w mars hydro led. Good call.