Hey, it happens! I had off days too when I didn't eat that much, it's just the overall pattern of your diet you're looking at. You are still good to go for next month!!
Tuna salad sandwich is just a can of drained tuna (I think the kind in water tastes better, not the oil kind, but whatever you prefer), mixed with either mayo, Miracle Whip, or 1000 Island dressing, depending on which you prefer, until it's a spreadable consistency. You can toss in a little chopped onion, celery, and pickle (both sweet and dill are good, whichever you like). Then just put however much you like on whole wheat bread or toast (I usu. use half on one sandwich, but my oldest son will eat TWO cans on one sandwich haha) add some lettuce, sprouts, and/or tomato if you want and that's that! But it's still good with just the tuna and dressing if that's all you have.
We also make "tuna melts" which is the exact same thing only with cheese and heated in the microwave until it melts but obviously anyone avoiding dairy will want to skip that one.

