That is exactly what it looks like. But, from what I can tell from the pics, it's only occurring on your oldest fan leaves which is pretty normal, in my experience. Your pH is a little bit low, but just barely. You might start using water that is buffered to the high side (6.6-6.8, maybe as high as 7.0, but I'd stay below that... I get nervous outside that range). Honestly, I wouldn't do anything, but my plants are not going to be featured in High Times any time soon.
Muddy may suggest something more aggressive. If he does, I would listen to him.