OP here.
I left off some details that I thought were irrelevant to avoid a wall of text. However with some criticism towards me, I am feeling defensive. Don't know why I care to get on here and defend my anonymous self against anonymous criticism but here goes:
The girl in question tripled during early lowkey meet because she had no competition in any of the events. It was basically three time trials. Four schools were there with maybe 20 parents in bleachers. I tend to do this early season to set marks in each event for athletes who haven't competed at these distances in a year. In fact, I like athlete early season running event tired to get base time so that when she runs it fresh next time, her time is better and she gets psychological lift. I find too many teenage girl runners have their self-esteem tied to their performance times.
Since then, she never tripled. She would alternate doubling with 1600/800 or else soloing 3200. Usually raced once a week; ran one other workout a week. Runs 35 mpw. Last year ran 30mpw but did tail off badly last 2 weeks of season (hmm?).
Over last six weeks:
1600: 5:01 (solo), 5:03 (solo), 5:13 (solo), 5:17 - gritted out win.
800: 2:17 (solo), 2:20 (solo), 2:22 (close win), 2:23 - gritted out win
3200: 11:01 (solo), 11:27 (close win), 11:45 - gritted out win
At district championship she tripled in order to qualify for Regionals in all three events so that she could then choose which to focus on for States compared to the qualifying competition.
At no time was I "chasing points" or "putting points ahead of girl's health." In fact, my first thought was her performance looked like someone who was running hard intervals prior to season and came in at peak form and subsequently declined. Since we didn't run hard intervals prior to start of season, I questioned her about training outside of practice. The girl she barely beat in 1600 and 3200 was her teammate who has always been slower than her. In fact, her teammate didn't speed up much during season, my top girl faded back to the other's time.
It was only after this last performance looking at the grimacing that I thought something other than "teenagerism" is going on; I recommended to her parents to have lab drawn. The reason I posted was to get other's input since I had never faced significant anemia in one of my athletes (that I know of; I've had plenty slow down for one reason or another). I don't "presume to give medical recommendations to a doctor" but the doctor left it to the parents to decide on oral or IV iron. I thought I would ask around for other's experience.