Today was a very crappy day and I feel like it's my fault

My (18F) parents (43F and 47M) seem to have woken up on the wrong side of the bed today and I feel like an asshole for doing things that are normally okay on every other day.

We were supposed to go shopping today because we're basically out of everything to make a meal (meat, milk, veggies, fruit...) and we're also out of cat food which is stressing me out. My stepdad was supposed to go shopping today because he has all the money (my mom won't get paid until Wednesday) but for some reason changed his mind. This bothered me because my mom is currently having a minor problem with her knees and ankles due to her peri-menopause and yesterday was really bad, plus she doesn't have any money at the moment due to a mixture of rent, bills, car issues, and her work changing her payment schedule so she wasn't paid on time.

At the time of writing this, it is currently 6:50 PM and we still haven't went shopping yet and I'm awkwardly trying to get my mom or even my stepdad to go since we really need cat food due running out yesterday so my cat is only eating wet food near the end of the day which makes me feel horrible. Asking my mom made her annoyed since she didn't really want to go today due to her knees hurting like hell and it being late (which wouldn't be an issue if we went earlier), but still got ready so she could at least pick up milk and cat food since that's all she can afford until Wednesday. My stepdad then asks, after her saying why she was only getting two things, if she was going to get everything on the list which made everything tense since she just explained why she isn't getting much tonight.

My stepdad has been snappy all day today, simple questions and statements getting him riled up (Ex. I noticed he was getting attacked while talking to a NPC and I mentioned it and he snapped saying "I know, Sherlock" which made my mom snap at him back). He would say similar things to that throughout the day which made me feel like shit because I wasn't trying to get on his bad side or trying to be mean. Like if I talked like that they would tell me to knock it off and just deal with it, but when my stepdad does it and we tell him to stop he gets defensive and pins us being bothered by his tone all on us.

Now my parents are arguing over groceries and my stepdad's attitude and I feel it's my fault because I asked about if we're shopping today last and I triggered my stepdad near the same span of minutes. I know it isn't my fault, they didn't really do anything to make me believe that it is, but I still feel shitty about it. I hate it when they argue because it makes everything weird and reminds me of my mom's previous relationship which ended with a lot of shouting. I tried to talk to my mom about it before, but I don't think she understands why it bothers me a lot.

What sucks is that they're not always in these moods and are often chill. When my stepdad gets annoyed, my mom is normally calm enough to help him relax and vise versa, but today is one of those days where everything shitty that has happened the past few days builds up and everyone is annoying and angry at each other and it keeps on building up until one of them gets pushed. Doesn't help that my stepbrother (21M) recently moved and he is practically eating us out of a house and a home without any effort to get a job which his stressing everything out since it's close to the holidays and the cold season.