spots yellow brown

These are autoflowers going for 36th day. I grow in a growtent with 400W HPS, reflector and air circulation. Soil with turf and perlite in smartpots. I use Canna Terra Vega nutes and this is my 4th time growing. Never seen anything like this and this has affected like 4-5 plants, started from...

Hey, been reading the forum for some time now and started my first couple of plants from bag seed 4-6 weeks ago. They've been doing pretty good until now. I have some yellow/brown spots on some of the leaves. I will include pictures. Around some of the smaller spots, there is a whitish area...