Answer: Wow - that is an investment you'll want to protect! If your part of OK is gripped in the current heat wave, I'm not surprised the trees (and you!) are stressed. Newly planted trees need even soil moisture throughout their first year to ensure they get well established. The key is to water soil to the point where it maintains a reasonable balance of moisture and air. Too much or too little water result in roots' inability to draw what the plants need. If you haven't already mulched the soil, apply a few inches of bark or other organic material. Contact the nursery that sold you the trees, and find out what their guarantee policy is. Since two out of the six are dying, there may be another problem that they can help you with.
As for mites, you can detect their presence with a magnifying glass. Check your trees regularly, since mites thrive in dry weather, and by the time you see symptoms (mottled, spotted, yellowing needles) a lot of damage has already occured. It's important to spray only if they're there. Best of luck!
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