The fungus you had growing on top of your soil + what you describe = overwatering, yup, ya did it mate, gotta increase the intervals between waterings, i let mine get a full day of completely dry soil before i water again. If i don't tips will start going down too over the course of the week.
Hope it really helps, if it does feel free to support back by picking the grow answer, it helps deeply in grower of the month contest.
Thanks and gl growmie.