spots/discoloration spreading

What type of medium; hydro
Indoors or outdoors?: indoors
What strain?: bagseed
How old are the plants? 3 weeks
What type of lights and how many watts? 4 6500k cfls, about 80 watts total
How far from the lights? 1-2 inches
What is your watering frequency and source of water? tap water that sits out for 24-48 hours
What, how much and when was it fed? NPK? dyna-gro liquid grow 7-9-5
What is the medium/runoff pH and PPM if in hydro? ph ranges from about 5-6.5, i use the drops to test it because my ph meter broke so i can't be exact, i started it closer to 6.5 and within the last week have tried to bring it down closer to 5.5 but i suppose it could be as low as 5.0, ppm started at about 200 at 10-12 days in, and was upped to about 400 about 17 days in(but my tap water starts at 125 so about 75 from nutes at first up to 275 now)
What are the temps and humidity in the room? dont have a thermometer/hygrometer yet, but the room is mid 70s, general indoor room temps and my pc case i grow in doesn't seem to get much hotter if at all, even at less than 1 inch from the lights my leaves dont get burnt unless they're touching the bulb
Any bugs? Look real close. none that i can see but no magnifying glass
Any other pertinent info?: when my first plant got to its third set of leaves the first set had small orange rust type spots, and slowly started progessing to the rest of the leaves but at a much slower rate than new growth was coming in, but now it seems to be getting worse(spreading to new growth) and changed to a more brownish color in most cases

 

nope just the dyna-gro for now, wont be able to get anything else for a week or two, it does have magnesium at .5 and manganese at .05 in it, should lower my dosage back down and see how it goes then bump it up if the problem gets worse? should i cut off some of the lower leaves that have gotten bad? they're drooping like they're not getting much light anyways and they're pretty shaded cause of all the new growth

 

thanks, really appreciate it, a few of the leaves are slightly curled upwards on the outside, but its mainly on the newer ones and i dont know if thats just cause they haven't finished growing and spreading out to their full size, though i do wanna lead more towards the mag deficiency than nute burn

i'll monitor it over the next few days and see how it gets +rep for the help

 

after looking at ph lockout charts i'm leaning even more towards a mag deficiency but possibly caused by ph problems(instead of lack of mag in the nutes) which would make sense as to why its getting worse, the low amounts of mag in the dyna-gro could very well been stopping the deficiency from getting bad but when i upped the ppm it dropped my ph down to the 5-5.5 range which some charts show to be low enough to lockout(or atleast reduce) mag intake

my ph tends not to drift with my dyna-gro nutes so i dont get the "benefit" of ph fluctuating and rising as nutes are taken that alot of other people get

i'm mainly just thinking out loud now incase anyone else comes through this thread with similar issues, hopefully this can help someone else also