help brown spots on lower leaves

im in my second week of veg. lower leaves are getting brown spots on them and some r turning yellow on the ends. ph is 5.8 ec is 1.2-1.4 im using botonicare power plant, blast off, cal mag and hydroguard all at 40% strength. my 1000 w hps is 28 in away from tops . good air circulation . the new vegatation is looking good though .i am using ebb and flow and flooding 15min 4 times a day. i wish i could post pics but wont be able to until next week. any help would be really great ful. thanks in advance

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do you have a tds? whats your ppm at?

Check the underside of the leaves for bugs...look closely. I didn't notice bugs until they were on the thermometer.

if there are bugs then there are multi-bug-killing sprays available

I had massive yellowing and brown spots before i realized it was caused by bugs.