Pedialyte and reflux question

My son has a high fever and diarrhea. He’s also very congested. Pedi said to do 4oz formula and 2oz pedialyte in each bottle. The pedialyte seems to be making his reflux flare, any experience with this? When I don’t put pedialyte in his bottle he won’t eat b/c of mucous and congestion, but he doesn’t arch and cry. Can I dilute the formula with plain water so he can eat and not have a reflux flare? Any suggestions would be great!! Also, do I need to space pedialyte from nexium? If I do this he won’t more than an ounce after his nexium (which isn’t a full meal). Please help!!