Dark shiny clawing down yep tox... but looks OK now. The serrations and cupping is likely leaf temps and light. Sometimes serrations will spike with a sligh mag deficiency. If the clawing is not on new leaves then it's a past N tox... especially if it's on older leaves. I see some K but likely due to transpiration of those leaves with heat/light stress.There are lots of tips clawed downwards, look at the last pic on that leaf in the centre of the photo. All the serated edges along the sides are doing a upwards "taco" and cupping upwards but there are many leaf tips clawing down. They are also becoming rather dark green + shiny.