Sick Platy?

[thisguyek]

I have a platy thats a little over a year old now and over the past few days I've noticed that it hangs on the bottom most of the time. every feeding time though he approaches eagerly, but everything it takes in it spits back out immediately. I've noticed a 'milky-ish' poop lately too.

any suggestions?

water quality is above acceptable, water changes (25% or so) weekly. temp roughly 74.

From what i can tell, there are really no physical signs of disease...