Need help! What is this spot on my phal leaf?

[buckeyetotoro]

Hi everyone. This is my first post but I've been checking this site quite often. You guys are great! I've been buying half-dead Phals from Lowe's (it has become my hobby/addiction!) and growing them for about 2 years. Thanks to your advice, I've been doing quite well,l though I killed some...
Today I found one weird spot on one of the leaves of the phal I recently purchased from Lowe's, and I'm quite concerned about this. I've never seen this spot - it's sort of yellow at the center with a darkish green ring around it. This spot is somewhat translucent. I've been checking on the internet like crazy, and I'm afraid it could be erwinia??? If you can help me, I'd truly appreciate it. I'll attach two photos - one from the top and one from the bottom. Thank you so much!