Nail problems and nutritional deficiencies post esophagectomy

Hi. My husband, 64yrs, is 2.5 yrs post Ivor Lewis esophagectomy for adenocardinoma of the esophagus and EGJ (T3 N1 MO). He’s feeling really well in general, working normally, exercising and eating fairly normally apart from smaller portions and lower carb diet due to occasional dumping syndrome. Recent scans all clear. However, he seems to have a few malabsorption issues. He’s taking Creon for fat malabsorption. He’s got slight iron deficiency anemia so is on iron pills and spray with Vit C spray. They’ve said IV iron not necessary. B12 normal but he’s also on B12 and Vit D sprays to keep levels up. He started getting cramps and Magnesium supplements seem to have helped with that. However, recently he’s developed very weak, flaky nails and I’m worried that it may just be one external sign of a more widespread deficiency that could affect the bones (osteoporosis etc) and other organs. Does anyone here have experience with signs of flaky nails and which supplements were you given to combat that? I’ve looked it up and seems zinc could be one of the culprits but it’s hard to measure in any blood test and any supplements may also not be absorbed well. He will go back to the esophageal surgical team after the holidays to ask for advice but not sure if it’s them or a dermatologist or another specialist who’d be the right one to go to.