Brown patches on some fan leaves (pics), need help!

Hey,

check out my post from my grow journal where I have a picture of it.

https://www.rollitup.org/grow-journals/374512-my-first-ever-grow-unknown-2.html#post4982706

Dunno what it is, only some leaves have it. Worried it might be some type of disease but it also might be a nutrient burn from the 15-30-15 I gave them last night.

Any ideas? Will rep

Nutrient burn seems likely

my guess is overwatering.

I had the same problem with my leaves a few weeks ago the tips of a few of the fan leaves were curling upwards and they were brown. They seam to be a little better now that I cut back on the water.
I havent used any nuits tho, I have been using my fishtank water and it seems to be working wonderfully. I dont understand the nutes at all lol