depending on how many leaf are like that, i personally wouldnt worry too much. just make sure you shake your nutrients well before mixing and mix well. Add one then mix, add one then mix. (but you know all that.. ) as long as the water is "good" thats all you can do
I will assume this is the worst leaf people don't want to hear this but honestly a lot of very minor problems like this end up correcting themselves from my experience. If it doesn't look too bad just let it go check on it daily to see if the problem has progressed and if it gets a little bit worse then treat it, remember to much love kills.