Room, lots of food, aeration from the wind, sunshine, plants to nibble rotifers and other microfoods and "water changes" via the weather evidentally make for very robust fish!

You sound like you are really on your way to doing well with them. Phry has some good advice to consider too.

Guppies are browsers by the way. At least partly vegetarians, they are always looking for food. (Omnivors, like herbivors, have an intestinal tract longer than their body length and need to work to keep it full.) If possible (do as I say, not as I do) several small feedings a day are better than one big feeding. Some of the show guppy breeders actually feed them five times a day. Others have set up an automatic feeder - a container of baby brine shrimp and a valve on a timer. That tiny valve opens for a few seconds every hour and dumps live baby brine shrimp into a tank. (A lot of water is changed to keep the salt level reasonable.)

Time challenged people like me (that sounds better than disorganized people) have been known to put a couple of fry in a daphnia culture. They eat what the daphnia (a freshwater crustacean which is very important in many food chains) are eating. Later they can eat the baby daphnia. They grow very quickly when literally swimming in food.

The daphnia life cycle is similar to that of the brine shrimp (Artemia species, several of them actually). Brine shrimp and daphnia are members of a large group of small crustaceans called claudocerans. There are several species and genus of Daphnia too. Both groups of animals are opportunistic filter feeders. In good times, females will parthenogenically (without sex) produce more females.

In bad times (drought, cold, heat, food depletion) they will produce both males and females. Those will sexually produce cysts or resting eggs. Daphnia eggs over winter here where ever the adult resided. In salt lakes people collect brine shrimp cysts by the tons. We know them as brine shrimp eggs.