To me those look to be from friction. Tears, rips, missing pieces etc. I've seen this from having to heavy air flow in spots.There may be something else going on but for me it's to early to tell if/what it is. I would just suggest for now to make sure your pH is dialed in and if the tips continue to burn any more dial back your feed a bit. They don't look bad at all. Looks like they are recovering pretty well from the topping.