THIS IS NITROGEN TOXICITY!!!! You don't give any information in your diary about the nutes you're giving her but you're giving her WAY too much nitrogen and may have created a lockout. Have you checked the PH of your runoff (do you even HAVE runoff when you water? It doesn't look like it, tbh but you should ... it helps clean out the soil so the nutes don't build up and lock out the plant's ability to take up nutrients)... PH of what you give her (both water and feed) should be between 6.0 and 6.5 as should the runoff (when you water, you need to try for a 10-20% runoff and test that water). If you don't have a PH pen, I've got to tell you that's the ONE tool that I wish I had invested in very early in my growing ... Just get one - it solves and avoids SO many problems.
Your pot size is fine - I've grown a number of autos in 5 gallon pots and they tend to be larger plants because of it (I'm always doing experiements trying to figure out what MY perfect size pot it). But since it doesn't look like you're giving it a LOT of water, I would recommend doing a small flush.... clear out the nutrients that have built up and get the plant back to a good ph range. A normal flush is to run 3x the amount of water through the pot as the pot size - so growing in a 5 gallon, you would run 15 gallons of water through her. I don't think you have to do all of that since your watering has been minimal (by the time my autos are the size yours is, I'm making sure the entire pot is watered...) - I would tell you to run at least 3 gallons of ph'd water through her and then let her dry out before you start your nutes again... and when you DO re-start your nutes, only give it 1/2 strength. Always follow the water/feed/water/feed schedule (some do 2 waters/1 feed/2 waters/ 1 feed - but I like simple alternating). And ALWAYS make sure your PH is in that good range (6.3, btw, is the "sweet spot").
The biggest question I have for your grow is what are you feeding her? Autoflowers don't need a whole lot of nutes early in their life.... I only grow autos and hold off giving them ANYTHING until it's painfully obvious they need something... and then I start out about 1/4 strength... if the plant handles that, I increase to 1/2 strength... and on... But this particular plant is exhibiting a bad nitrogen toxicity ... it doesn't matter that the other ones may not be showing the same symptoms - each plant will react in their own way - one plant will tolerate it, another won't... which is one reason a lot of growers don't like autos!
Good luck... I'm glad you have somewhat of a diary - but try to put in as much information as you can as that will be really helpful if you run into problems/questions in the future.