Well, you should ALWAYS be checking your pH. It looks like you have some pH lockout, since the new growth is yellow as well, meaning you are out of the correct pH range to absorb nutrients. What has your feeding/ watering schedule been like? A few other things I will mention, that plant looks too big for that pot and might have been stunted because of that. Especially with the soils a few inches from the top, fill it up next time. Also, that string is too thin and might decapitate your plant as it stretches. I would try and switch those out asap!
So to recap,
Check pH often and adjust as needed
Fill the pot with soil, consider a bigger pot next time
Use gardening wire, not string to LST
Thanks I kind of thought the string was too small and I'll be purchasing a ph kit today once I get off. I filled the pot to the top when I first started the dirt just compacted together it's a autoflower and it's my first test run is why I strated off in that small pot plus limited space but thanks very much for your reply I'm very grateful
You need to flush out the soil to get it correctly pH'd again. So put 3-5 times the amount of water that the pot can hold. So get what ever water source you use, use pH up or down to get it to 6.5 and then flush the soil. The idea here is to rid the soil of salts and build ups and reset the pH to a correct range. I check the pH of the runoff at the middle and the end to make sure it's sitting correctly.
I agree with the flush, get the ph correct. Then feed 1/4 the nukes. Resent experience with auto's. I made a lot of mistakes PH was one that had to be corrected before the other could be addressed. Auto don't like a lot of nutriunts.
PH the water going in to 5.8 to 6.0 I shoot for 5.8. PH the water coming out. It should be 6.0 to 6.5, I shoot for somewhere in the middle 6.2 As long as you keep the medium between 5.5 and 6.5 you should be ok. 5.5 just seems a little low to me . that why my input PH of 5.8
It appears you have a phosphorous deficiency unless you were experiencing lock out, otherwise you could improve that growth and flower formation by supplementing phosphorous. Yellowing like that can also occur from light bleaching. A friend had similar issues the other day from light bleaching, over watering, and phosphorous deficiency. I'm happy to report that all have been corrected.
Light bleaching can be caused by a grow light being too close to the plant, a grow light that was cheaply made or reaching the end of it's life span resulting in emission of a poor spectrum, or an indoor plant being moved outdoors. All result from oxidative stress induced in the plant by excess reactive oxygen species, typically oxygen radicals, resulting from elevated rates of photosynthesis.
It's water mixed with a sprinkle of foxfarm big bloom it's dry as hell in the box so I mist it every so often I have a fan blowing in and one pulling air out so the plant drys in about 2 minutes or so Ive read different point of views on misting so I figured what the hell lol its been working so far once the buds thicken up a little I'll stop thouhh