Older leaves will naturally yellow and die off so if it is just an old guy here and there no problem if it's effect several leaves at once you may have an issue. Got pics of the whole plant?
It didn't affect the entire plant I just mixed up waters when feeding noticed this when I went to top. 4 leaves total affected but only 2 really felt it but all new leaves have been healthy I just wanted to check others opinions on the topic. Thanks