Canker sores can be more frequent if deficient in zinc, Thiamin B1, Riboflavin B2, Pyridoxine B6, Cobalamine B12, Folate B9, iron and Vitamin D.   Following a low histamine paleo diet helps heal.  Mast cells in our body make histamine and release it as a part of the inflammation process.  Foods that contain high histamine levels can make inflammation worse.  Mast cells get "itchy triggers" and can release histamine when exposed to some spices and foods.  The vitamins listed above are also required to clear histamine along with Vitamin C.  Following a low histamine diet like @Mari and @Blue Roanand keeping a food journal like @Blue Roan does are excellent ways to travel on our Celiac journey.

Nature Made B-Complex (Costco) contains 2mg of B6, which is close to the RDA for it.

@dlaino, Which symptoms are getting worse for you?   Which vitamins do you take?   Do you take Vitamin D?

Hello, @Lightingthunder2, I understand how confusing Celiac can be, especially when one develops other health problems. I developed Type Two Diabetes and was prescribed Metformin.  I started feeling weak and tired.  I searched for answers using my nutrition and microbiology education to find answers.   I learned that Metformin can cause Thiamin Vitamin B1 deficiency.  Metformin blocks the thiamin transporters that allow thiamin to enter cells.   Keep in mind that Celiac Disease causes poor absorption of all nutrients, vitamins and minerals that our bodies require daily to live.  Thiamin can be rapidly depleted because it cannot be stored for very long (3 - 21 days).  With Metformin blocking entry into cells and malabsorption from celiac disease, thiamine deficiency can set in quickly.  The early symptoms of thiamine insufficiency can be vague and easily be attributed to other things, like a bad day at work, and doctors can easily overlook the symptoms.  Doctors aren't well educated in nutritional deficiencies.  My doctors were clueless.   I took thiamin in the form Benfotiamine and followed the Autoimmune Paleo diet (developed by Dr. Sarah Ballentyne, a Celiac herself).  Benfotiamine has been shown to promote intestinal healing.  The Paleo diet cuts out most high carbohydrate foods.  This helps me keep my blood glucose levels under control without Metformin or other medications.  Now, I do add in occasionally rice or potatoes.  I avoid most gluten free processed foods since they are not enriched with vitamins like gluten containing products and are filled with saturated fats.  I do not take any pharmaceuticals for high blood glucose.  I control my type two diabetes with diet, and take Benfotiamine. Thiamine deficiency is found in both Type One and Type Two Diabetes.  Thiamin is not properly reabsorbed in the kidneys in both types.  Since thiamin is water soluble, it is lost easily in urine.  Type One Diabetes has a genetic component which involves thiamine transporters in cells not functioning properly due to faulty genetic information.  Type Two Diabetes may result as a consequence of thiamine insufficiency.  Ninety-eight percent of diabetics in both types are Thiamin deficient.   Discuss with your doctor and Nutrutionist any dietary changes and supplementing with essential vitamins and minerals while you are healing. Here are some articles I found helpful.  Thiamine and diabetes: back to the future? https://pmc.ncbi.nlm.nih.gov/articles/PMC8505293/ The potential role of thiamine (vitamin B1) in diabetic complications https://pubmed.ncbi.nlm.nih.gov/18220605/ Thiamine Level in Type I and Type II Diabetes Mellitus Patients: A Comparative Study Focusing on Hematological and Biochemical Evaluations https://pubmed.ncbi.nlm.nih.gov/32528766/ Exploring the link between dietary thiamine and type 2 diabetes mellitus risk in US adults aged 45 years and older: Insights from a cross-sectional investigation https://pubmed.ncbi.nlm.nih.gov/39642136/ Metformin Is a Substrate and Inhibitor of the Human Thiamine Transporter, THTR-2 (SLC19A3) https://pubmed.ncbi.nlm.nih.gov/26528626/  

I'm not a gastro doctor, but it seems reasonable to conclude that they would be able to spot any cancer-related issues during the endoscopy, at least in the areas that were checked.