White Widow Autos (first-time grower)

Hopefully the nute burning has stopped for #1/#2. Luckily it hasn't hit the buds, but the other leaves and almost all dead/dying. Started using 25% nute level after a few waterings without nutes. After taking these pics, #2 got bad light burn in a matter of hours from the side light. It has almost no leaves left. Was algae/mold in the humidifier hurting the plants? Moldy smell and fungus gnats have gone away. I will clean humidifier more often, as it turned out to be very dirty. PH Down worked well when using 2ml/gal as opposed to 1ml/gal. Maybe the high readings were accurate after all, and it was PH lockout instead of nute burn. I'm surprised the plants don't smell yet. ________________________________________________________________________________________________________________________________________________________________ Looks like Plants #1/#2 stopped growing vertically (17" and 20"), so hopefully buds start to fatten. Plant #3: Leaves started yellowing/rusting today, just like how #1/#2 started. I don't know how this could be nute burn since I've been barely giving any. Plant #4: No issues but not really growing, either