Is it bad not to ask previous PI for LOR?

[mchammer]

I've been working as an undergraduate in the same lab for the past three years and this fall I plan to apply for grad school. I know that the PI from my current lab will be willing to write me a strong LOR but I am struggling to decide who else to ask. I've had two other research experiences, each for 1 year long at my university. I could ask both of these PIs for LOR, but I honestly feel that there are other faculty members in my department and through my undergraduate research program that could speak more to my abilities and intentions and I think they would be happy to write letters. The mentorship I had at the other two labs were not as strong as what I have experienced in my main lab, and while I don't think these PIs would write weak letters, I think two other faculty members I've indirectly worked know me a bit more personally/academically.

Would it look weird to write about these experiences in my application but not have letters from labs where I've done research?

Edited September 4, 2019 by mchammer