When I had heartburn in chemo (on Pax) it was actually caused by the anti-sickness tablets, ondansetron, they gave me 6 a week and actually needed 1 or 2 I found in the end then heartburn stopped.
I didn't have much nausea or sickness on Pax at all and that's apparently the norm. I have a sickness phobia but actually took far less of the anti-sickness tablets than they told me to as had so little. I had no issues with nails but I put packs ice cubes on my nails / ice gloves each chemo - took in a coolbox from a camping shop each time and my nails were same as before. I also took ice lollies and no mouth issues. Got stronger prescription only toothpaste from dentist which helped, it was harsh on teeth and eyes for me. I did get bad neuropathy and had to take gaps and go down to 90% after 4 but got through all 12, symptoms worsened 3 months after chemo but then subsided and minimal neuropathy one year on, eyesight worse, teeth worse but still all there and dentist said good. Steroids were worse for me than the actual chemo, massive moodswings, extreme depression, ranting, though they can cut those and they did when I asked. I didn't do EC before and I found with Pax some effects after finishing so it could be EC effects continuing if similar to before. I had weekly Pax x 12.