Certified GKH Gardening Expert
It is definitely fungal. You can likely correct this by mixing 1/4 peroxide to 3/4 water next time you water it. This will only need to be done once, or any time that it is needed in the future.
Just make sure that the top 2 or 3 inches are completely dry between waterings. This is likely how the fungal infection came about, by being too wet for too long.
As far as the weeds, the largest is a dandelion, the other two have many lookalikes, and will be harder to distinguish at this age.