I am working on a project as an undergraduate researcher in Prof A's lab.
At the end of the semester, one of my class professors, Prof B, proposed an idea for a project, so I and a few other students volunteered to research with him. Since this is all over the summer (meaning no classes), the topic was interesting, and I have nothing to do due to the pandemic, I thought it was okay (time management isn't an issue). The work with Prof B isn't part of a dedicated lab either, and I expect it to last just a few months in the summer.
However I came across this question (https://academia.stackexchange.com/a/47981), and now I am concerned that I am lying by omission. How do I let Prof A know about Prof B, or should I even worry about this? Was it wrong of me to volunteer with Prof B this summer? My question is different because I have no other obligations.
The last thing I want is to worry Prof A or make him unnecessarily think that the lab is boring, or for him to get a bad impression of me. Time management isn't a problem, and I've been attending & contributing in all meetings and deadlines, etc.