It was possibly either powdery mildew (which ain't as fluffy as other things) or some kind of mold. You get rid of it by growing plants in better conditions (as you figured out!), with decent ventilation, and by lightly scraping off what's there when you make the other changes.

Some slow release fertilizer contain actual liquid inside the balls. You can literally “pop them” and liquid fertilizer will come out. They aren’t eggs, and i’ve seen some come in gray and yellow colours but i‘m sure the whole rainbow exists. Someone mentioned root nodules, which would only be the case if they were directly connected to the root and looked like a hard, solid tuber inside (these are common but not limited to alocasias and calatheas for example). Fungus gnat eggs are practically microscopic, and unless your plants have direct access to the outdoors it is unlikely (but still possible) for it to be snail or slug eggs. What most of you are seeing are simply slow release fertilizer, if it’s truly bothersome you can buy organic potting mix that doesn’t contain any. Any generic potting mix from your nursery or garden centre, such as promix and miracle grow will contain these fertilizer balls and likely already in the soil your plant comes in from the nursery or store. You can literally sift through your new bag of potting mix and find them. If you truly believe them to be eggs, again unlikely, scoop them out and wait for them to hatch lol. You probably will not have bug babies but maybe you can gain some peace of mind.

If someone makes their own soil-less mix (and millions of us do), the addition of gypsum is essential to the health of the plants. It's a great way to provide a couple of essential elements without putting the pH out of whack. Not a fan of the Epsom salts in containers. Anyway, your particular potting mix is one that cannot drain well. Those ingredients are fine for in-ground plantings, but not containers. The use of containers changes the entire workings of a soil/root system. Even the finest top soil can begin to act like the enemy within the confines of a container. Since the drainage is going to be poor, you can expect that kind of crystallization to form on the soil surface. If you were to get rid of some of the peat moss, the vermiculite, bone meal, cottonseed meal, Epsom salts, and top soil you'd have something you could work with.

its a soil borne mold . it doesnt affect plants. Indoor soil is usually made of soiless mix - meaning its organic materials like compost. If its too wet and there's not air circulation in the area - it gets that way. Happens a lot when I germinate plants indoors. You have a money plant I think.. and the leaf browning is probably because watering had been sporadic. In anycase, your plant looks root bound and so time to change pots. When root bound, water may not be able to escape because the roots have clogged up the drain holes. Water may remain at the surface unable to reach the roots which can cause drowning. It can also cause the roots to rot out (preventing water from reaching the leaves) So time for repotting and in doing so, get fresh new soil. I would suggest that you also add a bit of sand on top of the soil to prevent a repeat of the fungus.