HELP my Cory please!

Hi, everyone. I'm new to Fishlore but could use some help asap. We've had our 29 gal tank for about a year and a half and had only a pink gourami, pleco, and cory in it for the majority of that time. We recently added new fish and, unfortunately, didn't use a QT before adding them to our tank. We've lost a few of the new fish but, so far, none of our original inhabitants. We went out of town for the weekend and came back to our cory sporting a new head accessory. Can someone please help me ID this and provide suggestions on treatments? This cory survived the massive fish die-off we had in the first 6 months of having our tank and we'd hate to lose him.

 

Welcome to Fishlore
This might sound like an odd question but have you noticed any increased activity from the corys in the last couple of days?
I ask because from the picture it almost looks like a cory egg sticking to its head.
Any chance you could get a closer clear pic of the lump?

 

That was actually my first thought ("egg") because that's exactly what it looks like. We went out of town over the long weekend so we weren't here to observe any increase in activity, if there was any. We have this large cory plus 2 little panda corys we just got. Not sure who would've been the egg depositor, if that's what it is. And, on top of his head? It's just so strange. (I say "his" but really have no idea of this one's sex.)

 

From the pic it looks like a female & pandas aren't choosy about who they spawn with so an egg is possible.
Could you catch the sterbaI & see if you can roll it off?
Btw pandas & sterbaI have very different temperature requirements,

 

Coradee: I'll catch the sterba tonight and see if I can roll it off. Thanks for the input about the temp. We keep our tank right around 75F, which is the lower parameter for sterbaI but right in the range for pandas. We've had the pandas for about a month now and they are thriving so I think we're ok on temp compatibility. Thanks for the concern. If not an egg, any other suggestions?

 

Coradee: when I got home, the sphere was gone from the cory's head, but there is a little white spot remaining where the sphere was. Any ideas?