1st Grow Auto Blue Amnesia

No it is not preflowering. Now, the color is fine so stop worrying. What you can do is stop feeding it, it's too early, you will burn them. Also careful with over watering, 0.3 liters is enough for a week at that stage

Those tips are showing the start of nutrient burn. Also, the tips are curling down (drooping ends) which is usually a sign of Nitrogen toxicity. Feeding water is good, but ideally you just want to feed a very low ppm/ec of your Grow feed. The plants will still need nutes, just not as much as you've been giving them. ~300ppm/0.6EC is a good 'just water' measure. If your (tap?) water has high ppm, it might just be tap water. If it is low, you can squeeze some ppm's of your Grow feed with the 'just water'. Those blisters look like a ph issue, but your ph at 6.3 should be ok if a little high for veg. Try ph 6.0 to get rid of any more blistering as some strains get stressed more easily than others when the ph is not what they want. None of this is terminal and you have lots of veg time to nail it down :)