To me it looks like abit of nutrient burn . I've had this same issue. They then turn crispy . I'd back of abit and only use water for the next 2 or 3 days .
You should see the new growth not effected. The lowers will probably stay like that. Might eventually die off. Should be ok.
Leaves are too dark to be a deficiency, if anything id say there is too much phosphorus, but check the ph as well, shouldnt have that many 3 fingered leaves, that usually indicates an issue when that happens.