newbie problems

What's up everybody, this is my first post on here hope I can learn some stuff around here. My problem is this, my plant which is 10 days old trans-siberian auto, I've been dealing with what I believe is high ph and/or possibly a magnesium deficiency. My girls lower leaves turned yellowish at the tips and is now working its way up the plant, is this from a magnesium deficiency? As of yesterday I got ph up and down to fix my water, also the guy at the hydro shop recommended that I go ahead and mix 1tsp of grow big the next time I water it which I did last night. Now I'm paranoid that maybe 1tsp is too much for a autoflower this young, what do you think? This is my first time growing here's my grow info I'm using a 400watt hps at 75percent strength 16" above the plant, and im waiting on my white Ryder auto to sprout under some cfl lights before I move her under the hps. My medium is Fox farm ocean forrest mixed with 30 percent mix of perlite. Thanks ahead of time for the help

Here's some pictures

I doubt you had a deficiency this early on using FFOF. It could easily have been just your PH locking something out (looks the same. As a rule of thumb if you are having issues try just changing one thing at a time. In this case just adjusting pH then see how the plant reacts. You will probably be fine at that dosage, but FFOF already has nutes, so you could see a little burn from it. I would watch it a few days, if it looks like you have a little burn stick to plain water for a week than start using 1/4 of the recommended dosage of nutes, then ramp up to half then full. I did water/feed/water feed, some people do water/water/feed. Some plants want more, so there is no one size fits all answer, just take your time and do not do anything to rash.

The soil looks very wet, you may be over watering. What's your watering schedule? You should not be using nutes yet, should be enough in the soil.

that looks like nute burn. no way would you have diff now, she shouldn't even be on feed yet!

Thanks hhbum I will do that. I didn't mention but three days ago I flushed and transplanted it into ffof from moisture control miracle grow because that is when all this started so I'm sure the plant is stressed on top of all this I'll just have to be patient . I doubt it's been over watered and and Fox farm grow big is for the veg stage so that's why I have it... since its in the veg stage. It's still growing rapidly throughout the day so I'm guessing that's a good sign but it is is worrying me because its starting to spread to the younger leaves. Please anymore comments or opinions are more than welcome

Only watering every couple of days when the soil is dry 2" below the surface. in the pic here I watered it hours before so that may be why it appears to be overwatered

It will probably be fine. Just try to leave it be for awhile to let it adjust to all of the changes you have been doing. If you just put it in new soil I probably would not give it any nutes at all for 2-3 weeks. Then start off at 1/4 strength if you want. I know you want to try to do everything you can for your plant, but the #1 killer of plants is you Keep good lights on it and don't overwater it and you will both be fine.

FFOF is good for 28 days ( 4 weeks ) without adding nutes. That newbie plant only needs water right now and probably less water and less often than you what are currently doing.

Thanks I appreciate it my plant is looking a lot healthier today

That's great. Post some updated pics when you get a chance. Always love following others grows