Just another opinion to help you decide, I also think it’s fert/nute burn. Only judging by the picture, your leaves look pretty dark green.
Also a couple top leaves look like they have been bitten, or did you just tear/let the burnt tip fall off?
The yellow tips if nute/fert burn will gradually work it’s way up the plant to eventually affect the new growth in time.
You can wait and hope that the plant grows into the nutes you’ve supplied it with (I like to take the guess and hope work out of my grows personally)
You can try to “flush” the plant of the extra nutes which I’m not the biggest fan of considering my method of growing.
Or you check out your local nursery for an 18$ bag of organic soil and transplant it like you said you were anyway, this is what I would do personally.
I use freshwater with my plants and started using green farm innovations fertilizer and foliage spray (using pheno-gro) after I was having a similar problem - I also use master nursery bumper crop (growers mix) soil with a bit of Foxfarm seed starting soil to help aerate (I know I can use perilite and other shit but I don’t want to right now)
Hopefully this helps. Happy growing.
(Oh and point the fan toward a wall and bounce it back on the plant)
