well missing a day is fine since most fish need to not be feed for a few days before they even begin to starve. Its fine as long as you keep an eye on the water quality. Also a good diet of their food then just flakes might be a good idea as well. I feed my fish Blood worms and Brine shrimp as well.
I've been testing the Ammonia and Nitrite levels daily and I'm still doing daily water changes as they're new into the tank so I didn't want the ammonia to shoot through the roof!!
I've been cleaning a gravel a little whilst changing the water too so I'm hoping I'm keeping everything up to scratch!!

This is my first attempt at keeping Guppies - and I have to say that they're such lively little things - I was trying to get a water sample yesterday and they all swam to the surface and started crowding around my fingers!! Lol!
I was told to give them blood worms occasionally as a treat - is it ok to buy them frozen?? How often should I give them these??