Budding Prospects

Possibly to much nitrogen, your giving 3ml/L of a calmag product, if thats the recomended dose then fine but I haven't seen a calmag product say give that much, quite a lot of calmag products contain nitrogen so you may be over doing it.

No need to flush, its just border line N tox, nothing to worry about, do as others said and cut back the N a bit. Plants still need N in flower just not as much. Eg, if your giving a feed that's 4-4-4 in veg maybe alter that back to 2.5-5-8 or something like it in terms of NPK content. Good Luck!

It looks fine. 42 days is only six weeks and with four of them for veg she is only week two or three of flower. You can back off a bit if she looks dark but you will know when you over feed as the leaf tips will burn. As you are entering the bloom stage now you will slowly want to reduce nitrogen and increase phosphorus and potassium. The N is what will be making her look dark. Follow your schedule but you want to be introducing your ok boost and reducing the base soon.

You still have roughly 3 weeks to go, so don't get too excited yet. There is no need to drown your plants with gallons of water to "flush" them, this does nothing special. Just stop all nutrients/fertilizers 10-14 days before harvest and give plain water in normal amounts and at normal intervals, and the plant will "flush" itself naturally. For me, this means stopping feeding when there are about 95% brown pistils and harvesting when there are about 98-99% brown pistils.

you should just give them water from now on but actual "flushing" is not needed in my opinion sure you may be removing excess salts from the medium but its not doing anything to the plant itself people believe that flushing will strip excess salts etc from the plant itself however it does not work like that . if you want the plant to use up extra nutrients then just feed water and the plant will take what it requires via mobile nutrients from the leaves themselves