You fertilize them with every watering??? That is not required or recommended at all. Mint does not need that richness. I would suspect the fertilizer...the spots may be burns from it. Skip the fertilizer entirely.

With the purple? Your plant is stressed. If the colors are true in the image, there is something fundamentally wrong with the growing conditions. The plants should have an even almost medium green color not the pale color your plants have. See link. Not enough light or too much water would be the first culprits I would look to.

FataMorgana

Here is a link that might be useful: Google images

I suspect it's the potting mix/soil. What are you using?

Rodney

@Rodnet I use Earthgro Potting Soil.

@FataMorgana The pots I planted them in are self watering with a reservoir. I fill it with the miracle-gro. When it evaporates, going by what I leaned in Science, it doesn't carry all of the solution. Should I just put water in it and once a week add a miracle-gro solution? They were outside getting at least, 12, if not more, hours of sunlight. Though I have moved them indoors where there's non-direct sunlight since I posted this.

The amount of sun isn't a problem. I've got my mints in full sun and they do great.

I still have to say it's the potting soil. I've never used that brand but after doing a quick search about it, it's got some absolutely terrible reviews. Try changing to a better quality potting mix with one plant and see if it perks up.

And no, you don't have to fertilize every time. Once every few weeks of diluted fertilizer should be more than sufficient. Most herbs don't need much fertilizer to begin with.

Rodney

Here is a link that might be useful: Earthgro Potting Soil Reviews

Oh, it is diluted, It's not straight up fertilizer. I put a scoop of miracle-gro in a gallon of water and refill it a couple times before I add more. And I know what you mean by the poor reviews. I'm not exactly sure why there's many negative reviews on it as I haven't had any problems/complaints that others do. I'll try a different soil though. What would you recommend?

Also all my other plants are doing fine; perky, bright colors, just not the mints.

This post was edited by TehPirate on Sun, Aug 31, 14 at 15:40

1.) Leave out the chemical fertilizer entirely. The mint doesn't need it and neither do you. (I assume you intend to use the mint.)

2.) I'm not sure I understand your setup but is the soil always wet for the mint? If so, I go back to what I originally said, water and light are the two biggest reasons for ill-performing and light-colored plants here in this forum. If sunlight isn't the problem, I would look to water. Mint does not need to be soaking, setting in water constantly. Let the soil dry some between waterings.

FataMorgana