No, I think what @jmystro meant is that some issue in the root system caused that damage you see. Like a low pH situation caused the leaf tissue to not form properly and when pH came back into line normal growth resumed.

Since the old and new growth is looking normal, I would just keep an eye on it for now. It could have been a nutrient issue like Dude said. I get that sort of thing from time to time and I believe it is due to organic inputs not mixed in thoroughly enough. Or a pH issue like @jmystro stated.

Leaf deformities tend to to be caused by some type of root stress brought on quickly. Typically from an out of range pH or root pests.

Water temperature and O2 levels. High water temps and a lack of oxygen cause Pythium.