I'm seeking some advice about getting a fourth recommender. I'm applying to PhD programs in statistics and biostatistics. I asked my 3 recommenders, a PI and two former professors, back in June and they've all gotten their recommendations submitted.
Since June, though, I started a new position doing remote, part-time research in a lab that's related to my applied interest. I've been learning a lot and it's been a meaningful experience so far, but I've only been doing it for 3-4 months and part time at that. I've worked with the MS-level lab manager primarily and haven't really interacted with the MD PI at all. That said, the manager has several publications with the lab and indicated he would write a strong letter.
Would you all recommend getting a recommendation from the lab manager as a fourth recommendation to speak to this experience? I think it could help my application, but it could also dilute the current recommendations.
Thank you.