Critical Mass Auto (Big Buddah Seeds) 250w SCROG Soil-Coco-Perlite Grow

Hi everyone! I have some experience in cannabis cultivation, I have already harvested one lady, last year.
This year I started with 2 bagseeds, and the plants were O.K, but the genetics were not good and they would take 3 months or more in flowering stage ONLY.
I had the chance to get this Critical Mass Auto seeds, and I thought: Autos grow fast, really fast... 3 months is all they need to give me good buds! So I gave my plants away for a friend, and started this Not-Bag-Seed grow.
I apologize for my english, this is not my natural language, but I try my best!

SETUP

-DS60 grow tent ( Secret Jardin) 60x60x160cm
-MH 250w OSRAM for veg
-HPS 250w Phillips SON-T PLUS 33.000 lumens aproximately, for flower
-125mm CoolTube with a TT-125 exaust fan 280 cubic meter/hour

SOIL AND NUTES

-15 liter pots (the bigger one was filled with the same amount of soil as the small one)
-Soil was made with 30% potting soil for flowers, slightly high in nutrients. 40% perlite and 30% coco coir and fiber. Pretty good soil mix from what I have experienced. Also I added 3 tablespoons of dolomitic lime in each mix, to stable the ph...

-Iguana Grow and Bloom (Advanced Nutrients)
-Big Bud flowering estimulator ( also AA)
-Rapid Start ( for roots, made by General Hydroponics)
-Magnesium Sulfate ( You can find it at the drug store, it works as a laxative for humans haha, but gives magnesium for the plants)
-Digital PH meter.

ENVIRONMENT

Where I live, in this time of the year, its REALLY fckin* hot! From 28-32 C
The temps inside the grow go up to 34 C, but soon, the city will cool down!
(All growers from here hate this time of the year... Really difficult to keep temps cool...)
But, from what I have experienced, the plants dont feel thaaat bad with this temp, as long as there is a good airflow in the grow room! I can say that for sure!
RelativeHumidity ( RU) is around 60%, when it rains it goes up to 75%, 80%.
-------------------------------------------------------------------------------------------

The 2 babies sprouted 1 week ago, developed nice for 3 days, and then stunned growth, and started getting light green, or even yellow.

They are only gettting worse! The tip of one of the leafs, from onde of the seedlings is either burning ou drying... but juuust at the tip, almost invisible. PLEASE someone help me!!!!!

First off, I grow DWC only but it sure looks like you need to flush your soil, your small young plants really don't need much more than water right now, don't feed them until after they get a few more sets of leaves . Get them on some ph'd water only and spray the leaves with some water to send help faster to the leaves.