Deficiencies or nutrient burn help!!

Hello thank you for reading, My 2 plants are nearly 4 weeks old now and have started to brown on the ends and sides of the leafs, it has started from the bottom leafs and made its way up to higher leafs, I feed my plants once a week with nutrients and I'm not sure if it's receiving the correct balance, if my leafs are doing this because I've given them to much created "hot soil" or whether my plant is lacking in nutrients and is now suffering from deficiencies, I'm worried to top up anymore nutrients just incase, I will attach a photo and hope someone more experienced then my self will be able to help me with this issue, thank you

 

My medium is a light premix garden soil (it's not coco or perlite)
I treat my water to stay between 5.6 to 6
Havent tested any run of pH
My lights are 60whatts and hung about 4 inches above the plant
Atm the moment I'm using miricle grow (seemed to be working really well grew fast) that contains P, K nitrate, C and the other nutrients,
I'm very new to this so not sure if miricle grow was the best choice, I ordered some weed specific nutrients that are arriving tomorrow with different doses of nutrients because I thought the miricle grow might be the issue

 

The MG isn't the slow release kind luckily, when this specified nutrient solution arrives il be using that from now on, and I brought light soil because I had heard they need good drainage and breathing but next time il invest in some perlite to add in , if I now just use ph'd water to flush it do you have any idea on how many waters before I should start feeding again or how long it will take my plant to recover? (Also thank you for the advice so far guys )

 

Oh

Wow okay thanks for the gragh, I shall increase the pH to 6.5

 

Thanks for your help man, I've been worrying about it like crazy, good idea, il keep you updated with her recovery