Drake's library says white wispy mold on fermenting plant juice is fine and usually yeast. Avoid red or black mold. Pour off the liquid, not the top layer. (Office Hours Ep. 132, 42:16)
Your timing is normal. The recipe ferments for 3 to 14 days, and the warmer the air, the quicker it goes. Seven days at 23 to 27 Celsius sits inside that range. Pour off and keep the liquid in a breathable container. (KNF Demystified, p. 37)
Drake reads white mold on bamboo shoot and banana flower ferments as a sign fermentation finished abnormally fast. Move it into storage. (Office Hours Ep. 63, 59:52) The library says this for those ferments, not for fruit juice.
If mold keeps coming back, look at your jar. For a LAB ferment, the library blames too much airspace and too little sugar, meaning no sugar ring at the bottom. (Office Hours Ep. 49, 16:27) The library says this about LAB, not FFJ.
The library does not say how to tell yeast from harmful mold beyond color.
Sources
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