Depending on the maturity of your tank and the fishes natural diet an aquarium can provide a number of food sources on it's own. Platies for example also feed on algae and is omnivorous as also the preacox and cory is and most likely also has some algae on it's diet. But if they get hungry also can nibble on plants.. These are things to take in consideration, depending on which plants you have you could see some plant damage after a few days. Tetra's are known micropredators and reportedly most likely omnivorous as well as they take a wide range of foods offered. 🙂
Next to this, fish body temperatur is depending on its environment, the higher the temperature the higher their metabolisme and going with this also a higher food demand.
So obviously if you lower the tank temperature to the lowest possible will help a bit to lower their metabolism.
5 days is peanuts for a fish and in a well matured and well planted tank, there always will be something edible to find for an omnivore.. 🙂 I think you do not have to worry about that. But if you still feel different and worry a bit you could prepare them for the comming abstension with feeding them a good fat rich diet starting a few weeks before.. Like those grindal worm these are very rich in fat, aquarist who feeded this a little to often and to much even reported geting obese fish.