I know the blue fuzz might be a pest or mold. But I have no idea which it could be, so I was hoping someone could narrow it down for me before the mods delete this post. If there is a better subreddit for this type of plant health question, please let me know.

As for the condition of the plant itself: They havn't been doing great in the few weeks (maybe over a month?) that we've had them. They've been wilting a lot. We buy gerbera daisies every year and put them in the same spot (full sun, I've never measured how many hours, maybe 8?), and they've never been like this before. We don't measure the amount of water... we give them a good soaking once a week and ask the tenants to water them in between (yes, my mom is technically a landlord, which, according to reddit, makes her evil). The soil is kept moist and the pots have drainage. Anyway, in terms of sun and water, we're doing what we've done before - the only thing that has changed is soil. This year we used a mix of loam, peat, and compost. My mom thinks the soil is the problem, so she's having me repot them in store-bought potting mix. I was taking them out of the "bad" soil when I noticed the blue fuzz, and wondered if they had anything to do with the plant's condition. Honestly the plant looks fine to me at the moment, but I don't know much about plants.

What is this blue fuzz on these gerbera daisies?