if you've fertilized at all.. ease off.. stop for a bit.
you are at the mercy of what is in your soil... could try a soil slurry pH test and see if that's causing it? but, if somethign is in the roots, there's not much you can do outside. flushing the ground isn't going to do much, lol.
probably a little toxicity, if young, it'll get better... if robust and mature plant with these issues, that's more concerning.