Hi!
There is always a transition period in a revocery where a piggy is starting to eat but not yet fully. You need to continue to weigh daily at the same time (before breakfast is a good time as that is when the daily weight is at its lowest) so you can then tailor your top up feeding support accordingly and increase or reduce it at need. The loss of appetite from the baytril/enrofloxacin will continue for some days yet as antibiotics build up over several days until they reach optimal efficiency and they will gradually peter off again over several days. Meloxicam/metacam is an analgesic (painkiller+anti-inflammatory) but not a gut medication.
Please keep in mind that hay is the main food source making around 80% of what a piggy eats in a day; that is what your support feed is mainly replacing. A small bowl/ca. 50g of preferably green veg and 1 tablesppon of pellets per piggy per day are filling the supplementary role that wild forage used to have for those trace elements that are not contained in the very nutricious grass/hay fibre (fresh growing grass is high in vitamin C, by the way; hence why piggies have never had the need to make their own).
If symptoms recur after the antibiotic has worn off, please see your vet. Your piggy may need a longer course for UTI, may need checking for stones or sludge or may be suffering from a sterile (i.e. non-bacterial) interstitial (i.e. recurring) cystitis that cannot be healed with an antibiotic and can only be managed. The latter condition is mot much known outside vet circles that see a lot of guinea pigs but it has become increasingly more common over the last decade and is usually mainly diagnosed by default (low or no bacterial count) after all the other possible problems in the urinary tract have been excluded. Sterile IC can only be managed but not healed.
Right now, please concentrate on the transition and adjusting your supporting role according to how your piggy is eating on their own. Only the kitchen scales will tell you the up to date truth as you cannot control the crucial hay intake by eye alone.