Brown,Reddish spots all over seedlings

Hi, 1st time grower here, this is a GSC auto strain grown in soil for around 18 days and these spots came up after i gave them mild(1/4) root nutes 4 days ago.
The ph was around 6.6, it's a bit too high but also not sure if it was the cause of the problem. Only 2 out of the 5 seedlings had these and the other one only has a couple.
Any suggestions?

try to focus on the new growth .. they look healthy but i think your roots lack of oxygen ( mild overwatering symptoms, let the soil breath and get really lighter before you water again, especially with small plants in big container .. you want your roots to look for oxygen)
6.5 ph isnt too high in soil, these small spots could have been calcium deficiency, because of imbalances caused by soil too wet
let it dry before watering again and it will be fine

tyke1973 said:

Is any water getting splashed onto it during feed ,I would let it dry out before watering .It looks real light also what ec are ya at.

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About water splashing onto leaves. My nutrient rep said to use a foliar application with vitamins and micronutrients so I pre-wet the plants before watering. After I get feed on the wet leaves I spray another to rinse.
This Recommended Foliar: 5ml/L B-52 & 2ml/L CalMag