It's not a fungus. It is a form of cyanobacteria known as nostoc...kinda resembles seaweed :-) It is jelly-like when wet but forms those flattened, brownish-blackened discs when dry. It is a very common colonizer of nursery grown container plants and is likely where yours originated. It generally indicates an overly wet soil or potting mix or a lack of nutrients but it poses NO harm to your plants. Easy to scrape off.

So glad to learn that. Thank you!

fert is usually not a response to problems.. or perceived problems in the garden ...

are these box potted??? .... the clay pot colored blob in the first pic seems to indicate such ... if so ... potting media is a water management system ... and when it gets old ... it starts failing at water management ... and your pots can get swampy ... and as gal notes... thats not good ...

she goes on to say is might be a fert issue in pots ... but fert isnt going to fix a drainage problem ...

if you want us to go much further.. favor us with a pic of the plant ... and maybe your location might matter ... especially in regard to your leaf tips browning ...

ken