Guano is very strong (extremely high phosphorous) and giving it to such a small plant may be the cauase, especially if you splashed some on the leaves.
I would not be too worried, it will not effect anything, but I would avoid using guano at anything more than one fifth strength and no more often than every 3 weeks on a plant that size.
Anyway, it is not a fungal problem.
If you are a new grower, I suggest you visit the "Mandala Seeds" website and read their "grow guides", it has a huge amount of excellent information with a good focus on European products (and North American too)....you will find the grow guides most interesting!