You will know when you have brown jelly, it just oozes brown jelly.
If it does ooze, turkey baster it out and all the jelly will get sucked out.
It looks like your problem could be placement.
The top heads are opening and blocking the light from the lower one.
I have the same issue with one of my pieces.
You can either move it so all heads have equal access to the lighting, you can just leave it or you can frag it off.
Try the move first then see what happens.
Worst case scenario, that head dies....you still have (2) others.
Good luck.