not understanding why their bars are going down on the red
they healthy

Who much food do you have? If there is less then 400 in the bin, you could be starving them!

Or, what is their age? Maybe they are getting weak due to age.

3231 in food bin .. 48 is the oldest

You can check out some of what is going on with your villagers in the log file -- it gets overwritten every time you start the game, so open it immediately after you quit for the day.

The file should be located in the game folder: mine is called "ldwLog.txt", and you can open it with any text editor (notepad on windows, textedit on mac).

If your villagers are losing health, it will be recorded in this file somewhere -- for example:
Thu Aug 17 2006: Ariki got sick because of old age!
Thu Aug 17 2006: Ariki took disease damage. Remaining health: 5
Thu Aug 17 2006: Ariki died of old age.

(I took out time values to make the lines fit better)