I'm having trouble deciding on three people to ask for LOR. I have two professors I have done research with who are obvious choices but I am unsure who to select for my third LOR.
My school's campus has 2 universities on it. One professor I did research with is at the other school and one is at the school I graduated from. There is another professor I am close to that I took a class with at the other university who offered to write me a LOR on her own. However, I'm concerned that 2 of my 3 letters being from the other school will look odd. Important to note though is that I attended this school many years ago when I was less serious about college. I have since received an associates and then my B.S. since then.
My only other options are a prof. I asked at my school that seemed very lukewarm about it considering it was just one class I took with him and he's in the chemistry dept not the bio dept. I was also looking at a LOR from a respected veterinarian I work for at a large advanced animal hospital. I'm a certified vet tech and have a strong working relationship with the Dr but do not work directly for her, the hospital manager is also someone I think would be very willing but not well known like the Dr. I'm applying to PhD programs in ecology so I'm not sure if that is considered a relevant reference anyway.
I know at least one letter will be a really good one so how much should I worry about this third one?