Hi everybody, my sincere apologies in advance because I'm sure this is not a unique question or issue, however despite searching through the forums I was unable to find an answer. Perhaps I'm just not searching for the right thing.

Anyhow, I have a meyer lemon tree that's 2 or 3 years old now and it seems to be doing quite well. Back in the spring, you were all very helpful in identifying that a root stock sucker had nearly taken over my tree, and with calming me down! I pruned the sucker and while the tree seemed to be in dire straits for a while, it has bounced back and now looks better than ever, except for this one issue that's affecting a few leaves (maybe a dozen). I'm wondering if I've got a nutrient deficiency or something else going on.

The tree was outside all summer and I've just started to acclimate it to being back inside for the winter. We're getting pretty cold temps at night. I was gone for a lot of the summer and my DH was taking care of the tree, though by 'taking care of' I really mean 'watering when I reminded him to'. It was fertilized in the spring with a 12-4-8 fertilizer (not ideal, I know), and I don't think it got any other nutrients while I was gone. I've had a hard time finding anything locally that's a complete fertilization solution. I also occasionally add a bit of coffee grounds to the soil. The soil is nothing fancy. It's standard potting soil and I mixed in some mulch so it wasn't too dense.

I returned to find that some pest(s) had been munching on the leaves but the damage wasn't too severe. I know that katydids were one of the offenders. I also noticed that a few leaves were yellowing in the middle around the veins, and that some of the affected leaves had developed brown spots. The backs of the leaves look normal. I've included a couple of semi-close-ups of the leaves and a picture of the whole tree. What am I looking at here?

Here is a link that might be useful: Pictures are here