Ruff looking plant

i have 5 plants 4 of which are the same strain/clone. One of the 4 looks kinda bad. I’ve grown these strains multiple times and of the 4 three of them look perfect and one is sick. All of them get the same feeding, watering, conditions etc etc... any help would be appreciated. I harvested multiple times of this white widow strain with out any issues but this time one of them is doing this. The leaves are turning yellowish from the outside in. (Around the edges of the lead towards the center.) the tips are also burnt.
 

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