Kids sick all the time?

My boys are 2 & 3 years old and are literally sick with something or another every other week. It seems like if one is not sick the other is. We have had everything from RSV, to hand foot mouth, to covid, to ear infections, to stomach viruses, and just about everything else you can imagine in the last six months. I work from home (for myself) so it’s always been “not a biggie” to keep a sick kid home every once in a while… but at this point my business is struggling and I feel like I’m lucky if I get to work one or two days per week. I tell my husband this can’t be normal, people with regular jobs would never be able to pull off staying home this much with sick kids and keep their job. I’m starting to worry that my kids have something wrong with them that causes them to be sick this much. Dr says they’re fine but it’s just hard to believe. We keep a clean house, clean car, eat healthy, they spend plenty of time outside, I just can’t imagine what could be causing this. We have wondered if their preschool could be the issue, maybe not keeping things clean enough or teaching the kids practices that keep their germs to themselves??? Is this normal? Do I need to just shut down my business to keep them home and well??? It’s causing some major issues with me personally trying to balance what I need to do for the health of my children vs keeping our financial life in order running my business. I know some of you will have ideas or info that I don’t, please weigh in!!