Hello. At 12 day plants were transfered to bags an...

Leaves that curl under are mostly 2 things, to much Nitrogen, to much water. My favourite is to much water. 1,5 l water is a lot of stuff for an 3 weeks old plant. lift your pot, how heavy is it=? a plant in that stage would need around 500ml in 2 days, and if its qite warm alittle more. And the number andAmount of nutrients you give is to much . i see no need for a blooming fertiliser and only a little need for growing fertiliser. i would recommend you go give only 1 ml of growing fert. SkipTop max . bioheaven is ok. Ok short message... Give less water and fertiliser, Happy growing, have fun with yourDouble Grape
Rise the Humidity for ahealtheierplant with an Humifider.
http://www.just4growers.com/media/23631/vpd_2degree.gif.... this is a chart where you can see wich rh you should have in dependence to your temp and stage of grow

One more thing.. did you measure the PH of your feeding solution ( water +fertiliser)