yellow spots, advice appreciated.

Hi my first grow here all was going well, untill i recently moved them into a nft system about 3 days agao, this morning i noticed these yellowish spots on the new leaves, from reading the forums i think it may be a mag def, just looking for confermation of this or any other ideas and recomendations on how to fix it, thanks.

Plants are 3 weeks old, the nutes solution is 1.1ms/ec ph is 6.3, pump goes on for 20mins every 3 hours.

How good is your ventilation system? Im almost cirtain there is no problem here looks okay to me....could just be the move to the new system messed with them a little bit. I ask about the ventilation cause my new growth showed some light green like this and after I put in my ventilation system it went away.. could be a coincidence but it fixed the problem for me.

The ventilation isnt good at the moment, i thought the same thing and have left the door open all of today, thanks for your advice looks like i better oder some parts and sort out something more permanent.

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this helped me quite a bit, maybe ittl help you man

Ventilation seems to be the number one over looked thing in a grow room. I always had my tent door open but the thing is your girl needs fresh air and all youre doing is circulating old air. Watch I guarantee once you get your ventilation in youll see a burst of growth.

cheers for the photos really helpful, and yeah ill sort out some proper vent system, thanks