The plants turning brown is likely just them transitioning from their immersed condition to submerged. Plants are cultivated immersed, ie partially above water. This way the plants have ready access to CO2
, grow quicker, and are more commercially viable. You take that plant, put it in an aquarium where the CO2
is cut off, and the plants leaf structure will run out of carbon stores in the leaf and start to melt. New growth will be more tolerant to its new environment and this is what you should look for. You may lose all your original growth to leaf melt, so simply remove any dead and dying growth so the plant can focus on new growth.
The orange algae is likely diatoms, commonly called brown algae. Most newly set up aquariums go through a stage of having diatom blooms. They are feeding on out of balance nutrients in the water and tend to go away after a few weeks as the cycle establishes and these nutrients get used up.
The white fungus is probably mould. Could be coming from a few sources. Maybe its coming from driftwood, which is something im dealing with at the moment. Im just cleaning things up manually and its gradually getting better. How are you dosing ammonia in your cycle? If fishfood that also tends to go mouldy as it decomposes.