Vegative Leaf Tip Brown/Yellow Issues.

First of all.... This is an incredible forum you all have here, I am totally blown away by its resources available... That said I hope to get some help. (and I have seen similar things with respects to mine as well, but want to toss it up here anyway).

I am totally newbie, BUT know plants in general (hoticulture and Silvaculture etc from past years.) Most of everything makes very good sense, but ..(the BIG BUTT!!).

Room Temp - was 78 Degrees (I was told to drop it to 70 degrees, so I did). ??? I question what is truly best...?? (I hear 75 is the bullseye)
Potting soil - is "FoxFarm" - "Ocean Forest" (see picture).. I was told add no nutrients as this was perfect to grow in thru Vegative in (and also as the bag says).
Lighting - 4' long 8 Bulb T5 at about 6" above plants (on 24hrs)
Air flow - is good (brand new room custom built and set up for all the temp, air flow, humidity etc to be able to be dialed in to the enth degree)
Water - City tap water that has set in a bucket for at least 8 hours to remove chlorine and get it to room temprature.

This clone came to me from a grower that had just sprayed for spider mites 2 times, and is clean into my room from the pests.. I transpanted it into a 3 gallon buckte using the Foxfarm soil. (I note her that at the same time I added 2 clones from a local co-op under the exact same proceedure and they are fine, and growing like WEEDS) ;)

I notice the leaf curl downward, and the burnt tips showing me that it must have had nutrients added to it at the growers place I got it from.

He uses the exact same soils I am potting with and hasnt added any nutrients at all (according to him) He recomended my soil and told me.. DONT add anything until flowering...

So.... I have 4 plants doing great, and then this one doing poorly, and one other that is close to this bad... all with the same scenarios and nothing has been added to the soils????

Help???

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