Hey new grower here, everything has been going good. But the one plant that is my pride and joy and has made this worth wile is a monster compared to the rest but has recently had it’s leaves start to yellow/orange like a rust. I’ll include pictures, they’re really dry and brittle but don’t exactly break, been going for about a few days and seems to be getting worse! Really worried! It’s an auto flower, in fox farm happy frog, and I amended it with organic nutrients about a week ago. Followed all instructions normally. please let me know if you have any ideas on what it might be. I think some nutrient burn, but I don’t exactly know what I am doing as this is my first grow. ph is about 7 or less. Tried flushing a bit not a ton of h20 like gallons. Thanks so much!
I hate to ask this but what’s your soil pH? Do you know how to do a 1:1 slurry test? It looks like a pH issue. A slurry test is more accurate than runoff. Since you have a small window to collect runoff that will have any accuracy depending on how much you create. If it’s washing away low laying salts it’s invalid. Beginning of runoff discarded to fix that. Then at a certain point your just gonna be reading what you’re pouring in, invalid. So a slurry test is the best way to check this. 1 part distilled water to 1 grow medium mixed and let sit 24hr. Then check the pH of that. I’d run it through a coffee filter quick if using a cheap meter.
Or it’s calcium deficient. Ive just not seen it like that before. Let’s tag some people. @PurpNGold74 @Myfriendis410 @Deez @dbrn32
Trying to think of people usually pop in on Sundays.
Okay cool thanks for the help much appriciated. Just looked the slurry test up on youtube, ill try that asap. The ph is right around 7, though from the runoff like you said. Ill post a pic of the ph reading. I’ll check it again tonight when I add a few liters. It appears to be green with some yellow in the liquid also.
so you don’t think it’s a cal-mag issue, just wondering because that seems like a common indoor problem? And that was my next best guess for a solution to get cal-mag.
What was your amendment? I add salt nutrients and cal mag to my soil grows. More so when in heavy flower. Not much in veg. I use water filtered down under 20 ppm with no pH adjustments. Even if I add nutrients. Works for me but it’s the consensus it doesn’t work for most I guess. In a mixture of happy frog and ~15% extra perlite. May want to wait for people I tagged to chime in.
So my water reads about 7 before nutes too. Since there are hardly any solids to hold a pH. My water is also filtered largely beforehand. 80% of the time it’s 0-5
Welcome to the group! 
One thing I noticed in pic 3 & 4, the tips curling up would suggest light and or heat stress.
The other issue I would have is checking the PH with those drops, while some can use them successfully, most find them unreliable.
I would suggest getting the Apera 20 PH pen from Amazon. Between the light/heat stress and PH, you may have a lockout cituation.
Good luck! 
Yea that’s a good point as it grew so fast the light was quite close but I did move and dim it. I think that was a factor in this, but it seemed to start near the bottom or with older leaves (those are the primary points of concern w this). Idk if it’s just the light but yes definitely a factor. Thanks for the ph pen recommend I’ll check that out, any other ones that you like/trust ?! Thanks again.
Wondering what does one do for a lockout?!
Lockout is caused by too many nutrients and/or improper rootzone pH. Cannabis soils use dolomite and bacteria to help maintain proper rootzone pH. Those two things keep my plants pretty happy. But you may have ran into an issue.
Imo when it comes to a lockout I would mix 1 part hydrogen peroxide with 9 parts water to let soil breathe and depending on leaf color maybe get some powder bat guano to spread on soil. Overwatering is probably the number 1 issue for first time growers, root rot is a scary sight on gorgeous healthy plants!