could be heat stress and it could be bugs or too much nutrients too early in my opinion. I think the best course of action would be monitor your temps, do a preventative bug spray(I like neem oil, insecticidal soap, horticultural oil) to rule out bugs and heat stress, and if it were me, I’d keep a closer eye on PH and probably try to feed that one less, but that might be tricky without under feeding the others. the only time I’ve personally seen deformities like that, I had broad mites and or russet mites. Rule out possible causes one by one and you’ll figure it out.