toddler won’t eat

my 18mo daughter hasn’t wanted to eat in the last month almost at all. everyone says it’s normal as long as she’s drinking, but i didn’t know for how long this was considered normal. she will only have about 3 bites of something a day. everything else i offer her she either will take a bite and spit it out or not be interested at all. she’s also been extra tired and grumpy here lately. should i make her a doctor appointment just to be sure everything’s okay? i’m a young ftm with no one to really ask so any advice is appreciated