New growth tips yellowing :( helpppppp!

hello, newb here.

my set up

4 23w ecosmart cfls
lambert 100% organic potting soil with perlite
water every 2 or 3 days (when the pot gets to its original dry weight)
nutrients i use mg all purpose plant food (only dosed 3 times and very little maybe 1/3 of a cup)

well my problem is that the tips on my new growth are turning yellow. ive been reading online and it says if the new growth is whats yellowing i have a huge problem :'( i used to have a nitrogen deficiency but the mg nutes fixed that. i dont know what it can be and there is no other pics on google that look like whats happenng to my plant

please help me out

plant is 25 days old got the seed on 1/26/13

Anyone? Cmon help me

what is your ph at?

and when did you last feed to fix the nitrogen def....??

can i test it with a fishtank test kit ?

and maybe 2 weeks ago. im scared to add the mg i dont wanna over feed it.

Well I tested the tap water and it was at 8.8 using my fishtank test kit. I tested a gallon of purified water for babys at it is lower then 7.4 (test kit only has from 7.4 - 8. should I use the baby water?

Yeah and you can buy lemon juice i believe to lower PH......google it cheap easy way if you have no PH down people have how much to add to drop the PH .5 or whatever the incriment is !!! and honestly it should be lower than7.4 but yeah if it doesnt show you cant no

I tested the run off from the plant for Ph and it was below 7.4 ... I just added some miracle grow mixed with the baby water, hopefully it fixes the yellow tips.

You should probally ease up on that miracle grow bro I have grown with it before and it's known to yellow your leaves if you add too much or not enough water

How soon did you start with the MG?
I am in MG soil with MG perlite, and started with the all purpose at 25 days.
You need a better way to check your PH, it might just be a lockout.
Have you checked the PH of your tap water?View attachment 2533673

Im going with lockout, you need to check the ph of your run off water and then the PH of your soil and lastly the pH of ytour water to make sure everything is stable before you start treating something else.