Swollen Bellies on ONLY Platy Fry

Question
Hi Karen...As I was feeding my tanks this evening I noticed in my 20 gallon that my 5 week old platy fry had extremely swollen bellies.  There are 4 fry and all of them are swollen.  Until this evening, they have been very healthy, happy, and active.  This morning they appeared to be fine.  In this particular tank I have 2 male guppies, 4 female guppies, 1 peppered cory, and my 4 platy fry. (Momma was moved to the 55 gal.)  I've done the reading available on Dropsy and know there is basically no cure.  However, what is puzzling me is the fact that these fry did not one-at-a-time develop whatever this may be but all of them "swelled" at the exact same time????...just don't get it.  All other fish in the tank appear to be fine.  These fry were not as active when they were fed this evening.  Can you think of anything else that could be going on?  I have proper filtration, temp. regulation, aeration, and perform regular maintenance and water changes on this tank.  I have live plants and this is an established tank.  

Thank you for your time Karen,
Kim

Answer
Hi Kim,
My best guess is your platy fry have pigged out on some food. I would give them plenty of time for their little bellies to empty out. A day without feeding will be fine. I've seen this plenty of times with baby fish, they overeat and have swollen bellies, it may take a day or more for them to clear themselves out.

Best wishes and I hope this helps!
Karen~