Too much nutes? Help with brown spots

Hi Everyone,
I was just wondering what is causing this? I have 11 plants total and it is only on 3 of them. The tips of the leaves look good but down towards the stem of the leaf are some brown spots. The PH is 6.5 the nitrogen was low the potassium was good and the phos was low. I have been using miracle grow which is higher in Nit. and phos. These plants are in their 10th week of veg. Other than the brown areas on some of the plants they look pretty good to me. I was wondering if they are getting too many nutes. Any comments are appreciated. will post some pics

You're in the tenth week of veg?! Are you growing outdoors, lol?

In veg, your N needs to be high and your P and K need to be lower. Why is your nitrogen low in veg?