Canned tuna will work.
If you've not been following the meal plan exactly, can you give us a quick rundown of a typical day, w/ srving sizes included. And what were you eating before you started the meal plan. If you go from eating 2 meals a day at maintenance to eating 6 a day w/ higher calories, w/ no in between, you're going to likely add fat.
At your age, rather than "bulk" or "cut", we want to think in terms of "healthy", even if you have specific goals such as adding muscle or losing BF. And part of that is finding something that fits your schedule. So give us a bit more info and we'll see if we can help
BTW....welcome to IM