From what you posted your ph is to low. Its needs to be at 6.5 when you water in. I cant give you an exact reason what the bad leaves say and imo you probably have root issues now from what happened more than not, but this is what you do to fix it.
Flush out your pot with clean water phed at 6.5 at least two-three gallons shop vac all that up. Then renute at half strength add b-vitamins {superthrive} for the stress add microbes for any root issues and nutrient uptake. Add that mix to run off clean it all up and then leave it alone as far as watering anything else till the pot dries up. Pick off all the leaves that are 60% missing any green in them as they are trash and blocking light an any good leaves. You could get by without the b-vitamins but dont do this without the microbes in your water when you renute them.
You dont need to check ph runoff or do some sort of slurry test and get distracted with that stuff all you need is to know what you need to do to fix it and act on that and then you can go around and look at all the deficiency charts to figure out what had happened to your leaves if you want but what I told you is what you need to do to get it back on track.
