Is it normal for a 7 month baby to not want to eat baby food for 2 days, for no apparent reason?

Yes. Some children have very discriminating tastes and do not like the bland taste of baby foods. Some do not like a particular food. I encourage parents to make their own food. If you can mush it he can eat it. And mushed/pureed table food has more taste and fiber. Give one new food every three to four days. It will pass. If he is teething he may also be a little sore and just not want to eat.