Feeding goldfish is VERY bad. High risk of parasite transfer, no nutritional value. Goldfish also have high concentration of thiaminase, which blocks the cichlids ability to take in and process vitamin B. Can lead to neurological damage over time. A quality pellet should be an Oscars staple, fd krill, earthworms, mealworms, some spirulina based foods as treats. I also see some cratering on Oscars head, onset of hith. Do large frequent water changes. You have a nice big tank for the 2 cichlids, with quality care and the possibility of prolonged compatibility, you should have an enjoyable setup. A healthy Oscar wont starve itself, at the size of yours it can likely go 2 months without eating. Offer quality food, it will eat it eventually.