The meal worm looks like a left over uneaten, your bird didnt poop out a whole meal worm as it would have been digested and unrecognizable especially if your bird had the worms which strip your birds of all viatimins and nutrients and proteins producing the runs and watery stool. Sounds like you ahve a handle on it now and thats always a relief. There are a lot of good people on here with great advice as I have found out myself . Good luck with your birds they are amazing animals and fun to have around.