What is wrong with my cookies?

[Greengren1]

Yo!

Problem: Leaves are looking burnt/ some yellowing and curling. (Problem starts from the top of the plant)
Medium: Plagron light mix
Feed: Only given 1 feed with nutes 4 weeks ago (Sensi Bloom A & B @ 1ml per L) thats when the problem with the leaves started so I switched to just tap water. She has been drinking approx 850ml daily, with a little run off.
Strain: AutoColorado Cookies (50 days old)
Climate: 19.5oC - 25.5oC - RH 40-50%. Growing two plants in a 1.2x1.2x2.0m tent under an Advanced Diamond Series 200W led panel. For ventilation I am using a 4" inline duct fan and a rhino pro cf.

She has had this problem just a over a month now, it has been a really busy time at work for me and I just haven't been able to devote the time to her I would have liked. I am growing AutoBrooklyn Sunrise along side her and she is doing great, no problems at all. Any help would be much appreciated, this is my first grow and I am keen to learn what has happened to cookies so I can hopefully avoid it happening on future grows.

Many Thanks

[M_C]

Are you in a 'soft water' area?

[conrado]

Looks like a Cal/Mag deficiency...

[iwallace]

what size pots and where is the run off coming from, sides or bottom. 850ml of water aday dont seem right to me (im still learning so could be wrong)
the def im not sure so cant help you there,

[Bulls]

These is a great Auto feeding schedule by TaNg PeNg. He has great results using Plagron Light so you might want to take a look into this thread ->> https://www.thctalk.com/cannabis-foru...eding-schedule