it might not be true, check the age catagories of your professionals, often times they don't really make since, but that'd be the thing to check
i once had a 80M that was returned to me after i took a break, the intermitant owner sold pop from one of their other countries, and caused the pop neg effect, when it was sold back to me, the neg effect stopped, but the damage was done, and i had a huge pop bubble
i thought that if the GM pop was uniform in age groups, that by buying allot of population, it would smooth things out, i got to 160M before i gave up on that. so instead, i closed most my hospitals, for a sim-plague, and kill off all the weak citizens, that is the old, once my country more resembled a spring break community, i rebuilt my hospitals, but i had to retrain all my health workers. not a problem with that country, for some reason, that country, and only that one of my countries, just didn't work right with less than 200 EI, (i normally get along fine with 120,) so i was able to quickly rebuild my hospitals. how ever, several months latter, i noticed that i was loosing health care workers, at an alarming rate, so much so, that it was all i could to slow it down.
its just a thought that you did something similar, grew to fast, and now your feeling the backlash, best suggestion i have, raid some C3s, and as soon as you get them, close all the hospitals, then trade for what you need. eventually your professions will mello out.
buying pop might be a temp fix, but you'll need to over train while you are on top, to keep it under control, never tried it that way, so i couldn't tell you how much to over train. i don't like to have allot of those guys w/o jobs, so i usually run my EI priorities for them at 3-6, depending, maybe 7 for senior doctors, i'll usually run them 3-3-4, or 4-4-5 for cruising speed, and make adjustments as i need to, rarely ever have to make big adjustments