Yellow and Brown leaves - What's the issue and should I toss plant or defoliate?

[FreeTheTHC]

First time grower here! I've got three plants and two seem just fine but one has had some yellowing on leaves and brown spots for some time. It hasn't gotten dramatically worse, but it has spread a bit. I've read about septoria and also maybe nutrient deficiences. My tent is already pretty cramped, I was thinking to toss plant but wanted some feedback!

I realize I should probably do some defoliating, its my first grow, yield is not a concern, more successful grow is. I recently topped plants as height is a concern, I was thinking to NOT defoliate and just see what happened to learn, but now I'm worried. It looks like it might have even spread to another plant, but could be just a different issue (yellow leaf tip pic). I'd be willing to just toss plant or maybe give to a friend, but could defoliate and/or try nutrients. Its interesting the other plants are fine, but they are different genetics all three (the biggest is Auto, other 2x at reg fem and the yellow is White Widow).

What's your thoughts? Thanks for help and let me know if you need more info!

Growing in 2x2 tent
Coco Loco FF
1g Fabric Pots
Autowater base for a few weeks now, they seem to like it, drinking lots.

 

[LoveGrowingIt]

I wouldn't toss out the plant. Instead, I'd try to solve the problem to know what to do if it happens again. I don't think it's Septoria. Defoliating for air flow probably would be helpful, though. I'm thinking it could be a nitrogen deficiency, but I wouldn't rule out too much water, so letting the soil dry might help.

Also, a fan blowing on the leaves can cause necrosis at the leaf tips, so raising the fan might help.

 

[cj_aeratos]

Check the water ph

 

[Jeffdaman]

And take the leaf off I big leaf a lot

 

[Gmix]

If we threw out our plants every blemish we’d probably of never grown anything

 

[Bdubs]

I wouldn’t make durastic adjustments or do anything specific to the one than the other two. You are in soil so do a runout test and try to adjust your feed to that one to balance the Ph. You are obviously feeding what they want, that one is just having trouble eating some of what it needs probably due to nutrient availability through Ph. The medium is a buffer. It is possible the soil mix in the one pot is slightly different than the others. Causing it to retain salts or something in turn is off balance on Ph than the other two, given you are feeding the same nutrient mix to all plants.
Runout test, if the one is off from target, feed her last and adjust the Ph of the feed water specifically for her needs.

 

[Bdubs]

I see a lot of people call out mag and cal deficiency when they see the same leaf issue. But if you adjust that, you’ll likely realize it was an uptake availability issue and not a deficiency of total available nutrients.