whats wrong with my nute mixing gooey tan sludge

hi can anyone answer this for me this is what i do i use straight tap water its 350 ppm with ph 7.6 i know its quite high in both ppm an ph but i have never had problems before an still dont other than this mixing,
my ladies are 21 days old to day so nutes are low off reccomended dosage level.
now i fill a 50 gallon water butt with 25 gallons of water i let it sit 24 hours with a airstone in.
after it has areated for 24 hours
i add DM SILICA 30ml stir in leave for 30 mins,
next i add 25ml of DM ZONE mix an stir leave for 1 hour
next i add sensi grow A 150ml mix/stir leave for 30 mins then repeat with part B,
after this is mixed i then ph water to 5.4
now this is my batch ready for the morning when i do my change the problem is by the time morning comes there is this gooey sludge a light tan colour sitting in the bottom,
now i have mixed 4 differant batches an still the same results each time i have added airstone in there to areate an a powerhead for water movement an to keep nutes mixing still the same. Now if i take my ladies out of there system an mix the everything the same in the system i have no problems crystal clear water smells nice all good so what is the problem with the mixing in the tank
i thought maybe the nutes were precipitating or the calcium in my water was causing the phosphates to go wierd if i am on the right track any advice would be great

It sounds like some of your nutrients are falling out of the tank mix. No clue why it does not fall out when mixed directly in the reservoir. Is it a metal tank?

no there i mix them in one of these

as said if i mix the batch up exactly the same as i do in the water butt i have no problems pure crystal clear water,
i dont want to keep having to take the girls out the system everytime i want to change the nutes as i donot want to damage root system by tangling them or breaking off some of there feeder roots causing them to stunt for week or two.
they are only 21 days from seed an have about a foot an half length in roots an is hairier than cousin it from the adams family they are in a diy version of the current culture system, the growth rate is phenominal there at there 6-7th node are about 6-7 inch tall so real compact ladies.
i just cannot figure out why when mix nute batch up in tank it gets gooey sludge in the bottom of the tank that just sits there, as said i have tried putting powerhead in there for water movement air stone for aireation i am jus stuck an truly dumb founded by it

I know a man that has exactly the same problem as yourself gooey light tan sludge like snot, blocked all drippers and killed off roots. anyways what he is doing at the moment is.......
cannazyme to kill dead root crap, root juice to try and stimulate new root growth, rhizotonic to try and help through times of stress. . I am going to post myself for my mate and ask some advice follow if you like and ill explain his problem, very similar to yours.