mold is not the issue most people think it is (except slime mold which can be destructive), its part of the enclosure cycling, infact its an important marker to let you know that the cycle has started, and a good indicator of how well the cleaner crew populations and bacteria are building up.
Personally I would leave it for at least 6-8 weeks before thinking about changing it out, but first I would look at other things, like ventilation, humidity and substrate moisture content, plant foliage and root growth, and working out how much food is available (ie rotten vegetation, content of soil, dead cleaners) - all these things need to be in balance, and that takes time
molds and fungi means that the enclosure is beginning to cycle...patience is the key
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molds are only a major issue if they are out of control, or if they are in a sterile enclosure, rather than a bioactive one
You can use a clean damp sponge to remove some mold if you really want to, but you are removing food for the cleaner crews, which will mean they establish more slowly