Newb needs help!

First timer. Growing in soil and hydro. 400w hps supplemented with 2 48 inch flouros. Having problems with one plant in soil. Soil was prefertilized with osmocote 19-6-12. I know not ideal but all that was available when I started from seed. About a month old. Everything great until 3 days ago. Bottom leaves started tuning yellow with brown spots. Certain leaves are getting brown spots and it seems random as some are fine. Upper leaves are drooping. WTF? soil ph is between 6.5 and 7. air temp around 78. Relative humidity is around 55. Hydro ph around 5.5. but they are doing fine. even the other plants I have in the same soil mixture are fine. I noticed some tiny, tiny insects crawling on the outside of the pots but not on any of the plants. What is wrong with this one plant? I know the pics suck but so does my nephews 15 dollar iron man camera. It doesn't seem to like the hps at all. Any advice would be greatly appreciated.

what kinda ferts are you using sounds like nute burn prob a nitrogen overdose its the most common nute burn i think

its osmocote 19-6-12 so it is high in nitrogen but i have 6 others in the exact same soil with same level of nutes and they are fine thats why i'm confused.

idk maybe you should flush the plant and replant it wouldnt hurt but if its just on one or 2 leaves its not a big prob then.

dude for starters allways have good pics , there shithouse i cant see the problem lol , but im from aus and on my first grow i used that osmacoates soil with a 6month feed and i fried all my plants ...... but i was watering twice a day lol . i personally now will never buy soil with food release in it .