Yellowing 3 week old plants

I have a few purple power plants and they are looking a little yellow. Besides that they look really healthy. I feed them 1/4 strength mriacle gro 18-18-21. weekly. any suggestions what to add to green them up wouldbe helpful. Or do some strains look a little more yellow than others?

Without pictures it's a shot in the dark.
But, could be not enough nitrogen.

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Do u think the 1/4 strength weekly is not enough? They are in little pots that are designed to plant directly in the ground. Like cardboard. Should I fertilize more? I dont want to overfertilize

Honestly, I wouldn't advocate the use of Miracle-Gro on cannabis.

why not? Is there something u can recommend?

Well I've never seen anyone praise miracle-gro or show great results.
decent results for sure, but not great.
Miracle-gro in my opinion has been designed for outdoor flower hobbyist.
Our plant is a flower and also a weed.
There are many other choices for us growers, with products that have been conceived only for growers like us.
With our needs in mind there products perform better.
If Miracle-gro came out with a label that said "Cannabis Cuisine".
I would probably be more admit to try it.

I use FoxFarm Organic and I would recommend it to any grower.

thanks for the info

I am using miracle gro 18-18-21 tomato food cuz I read marajuana is grown similar to tomatoes. I was going to switch to bloom booster when they start to flower. Does that sound cool? There are so many different nutes is the problem.

I'm no expert on nutrients but,
you should try maybe giving them a stronger mix then you are now.
I would say that tomatoes are vegetables and cannabis is a flower,
too different in my opinion.
Flowering is still a long way away for outdoor.

ya thats why the fertilizer is 18-18-21. very close to all purpose mix. Thats what I heard is good for the vegetative stage. I heard that when it starts to flower switch to a flowering fertilizer. Should I boost the fertilzer to 1/2 strength or instead of feeding once a week go twice a week?

Both, scientifically the Tomato is a fruit, any plant containing seeds is a fruit but in culinary terms it is a vegetable. The U.S. courts (1883) have deemed the Tomato a vegetable for import/export reasons.

We're not arguing the validity of Tomatoes as a fruit or vegetable.
I am just pointing out that it's not a flower like cannabis.
Therefore we shouldn't feed it as such.