I read about folks on a plateau for several weeks and wondering what to do about it. I'll try to set this up as a sort of check list you can use although much will be paraphrased and abbreviated. DON'T GIVE UP - Your continued search will probably find the problem and correct it.
Many vitamin tablets have sugar fillers.
If you think it's too small to matter, better check again. Try it and see. Or a trace mineral shortage. TOO MUCH SALT - Salt or potassium shortages are common in the first stages of the diet. You may be allergic to some of them.