should i worry?

ok so the plant is around 3 weeks old maybe 4 from germination.
water temps between 18c and 20c.
room temps 22c-28c.
EC 0.58 and keeping rather stable only 0.01 drop in last two days.
PH 5.8-6.0
i use canna aqua vega, sensi cal-mag and some hydroguard.
i toppet the plant few days ago and took of the top sun leafs that shaded the lower tops maybe 4 days ago.
i started to notice few brownish spots 2 days ago and i would like some opinions in early phase of this thing so i can act quick if needed.
 

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