The, it just looks like a case of what's in your water, have you hard water? But yeah, it's from a few days of pouring water over your plant and with your light so far away it's drying so slow it's just leaving a white residue that's all, is that soil preloaded? If not, I'd start her on a light nute mix of 3-500ppm just a 100ml for the first wk. Then increase for wk 2 to 700 wk 5 and onwards start pushing it to 900. But if that's preloaded soil just use a micro and root stims if you have them, if you don't and using a canna mix it should be fine, looks light though, but if it's loaded apply nutes on wwk 4-5 depending how rich your soil is?. And try stop pouring water on top of the plant and around the stem don't let it be damp all the time, (risk of browning of the stem) very bad it's a plant killer, it looks fine though but pour to 1 side and stick to say 2 spots, try avoid wetting plant especially with aa nute mix. Also your light is very far away pal. The desired height which autos do best is around 30-40cm with your light. Best of luck, happy growing.