Blueberry zkittlez #1 - Royal Dwarf #2

It's slight light stress (light is too close / too bright) Every plant reacts differently or probably PPFD at each plant is different. Just swap plants and see if it helps.

They don't look to bad to me, a slight tacho on the biggest leaves, doesn't look like it's nutrient related, could be a bit of light or heat stress.

Maybe the humidity is to dry making her tips dry out

This is burning due to excess nitrogen/too much fertilizers............over feeding basically..............nothing more, nothing less.. Dwarf/baby plants need baby feeding. Your pots are too small too. This will cause salt build up quite rapidly, especially if you are not watering to get proper run off each and every time. Plants growing in quality, decent soil should not need fertilizing for roughly 4 weeks and then only with half strength to start with.

If I can guess I would say its ph related which is blocking the plants availability to absorb the feeds you are giving Magnesium deficiency is what I can see but if it is a ph lockout then it may also start to show other issues unless rectified

the readings you are refrenceing are from runoff yes? if your going in at 400 and its coming out at the numbers provided the first ones fine and the other two are getting overfed and you need more runoff.