The lowest/first leaves dying off is somewhat normal, I wouldn't stress too much, and some of the damage could be from hitting the string.
To me it is not a P/K issue, just typical low leaf behaviour and quite expected in my experience.
I put water until runoff around %10.. ph is always around 6.2~6.5. Humidity around 45~50. They appeared 2 days ago i dont understand why… I thought too it may be pk defiency?
underwatering and bad humidity could cause it too btw, its first leaf set. Till you screw up once - they are best indicators
Too little water makes N to go into salts and accumulation could arise , problems starts ...