Droppy Leaves, Need to worry ?

Hello there guys

Thanks for everyone that reads this thread, basically I would want to ask for your input on the situation of my 3-4 week mother plants in vegging.

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Top left is a Dutch Passion auto Blueberry
Top Middle is a Green House White Rhino
Top Right is a Nirvana White Widow (13 days)

Bottom 3 are all Green House White Widow.

I notice in particular the white rhino leaves are droppy (mostly the lower leaves) pretty much all day long, I water them 2 times for 15 minutes and they are in Rockwool, I use PowderFeeding nutrients all in one, from GreenHouse (seems pretty good, the nutrients and seeds were all gifts).

PPM:1450
Ph Is at 5.9-6.0
Temps: 28.2 Celcius/ 81-82 Fh
Lights:300 watt MH ( at 50 watt per plant)
Waterings: 2 x 15 minutes per day, Aeroponic
wind: blows all day (not agressively) but smooth
Humidity is 35-40%, but I notice that the sides where my humidifier delivers gets droppy leaves, (even if its in the other end of the growing tank) could this be a result of humidity or over watering, too much heat?

Overall I would like to know what do you think about my plants, and what are your Ganjack Holmes deductions. THanks very much

You say you're growing in rockwool, is that your primary medium, that is to say nothing else but rockwool? I get the feeling you are drowning your plants by feeding them for 15 minutes, you should just feed enough to soak the rockwool and let drain, in other words if you're using pump to feed, run it for only enough time to soak your rockwool, say 2 to 3 minutes, just my opinion.