I have had a ZZ plant for 1,5 years. It was already big when I got it. It grew a couple of leaves last spring. The old pot was changed in August 2020 and the new one is 12 liters with Lechuza PON substrate. Also, it was growing new leaves in December. Also, the ZZ is going to get a flower now.
I live in not a sunny place and now, in winter, there is little sunlight. At the end of December, I decided to use extra lights for the plant. I use 2 linear lights (85cm-12W-4000K-1000Lm and 105cm-16W-4000K-1400Lm), but the lights are bigger than the plant diameter and, I guess, only 60-75% of light flow reaches the plant. I used luxmeter app on the iPhone and it showed 300lx.
I watered the plant once every 4 weeks before using the light and once every 2 weeks now.
The plant dries out small old leaves.
Now I found some light spots on the leaves. I guess some conditions are not ok but don't know what exactly. Could you please help, I don't know what it is and what I should do with it now.