Ground Loops Galore (SPI Application)

i'm working on project has ics daisy chained through spi... , life of me cannot them communicate robustly.  after many hours, i've reduced of problems grounding scheme i've used project.  i've attached simple schematic showing current wiring scheme on same page.  know i've written lot of text here, i've bolded questions make little easier haha.  thank patience , help.

so first thing might notice how ics wired power , ground.  went scheme 2 reasons:
1.  cannot daisy chain power many ics.  amount of current builds each ic in chain, , 22awg wires , pcb traces cannot support current.
2.  lazy, , didn't want spend week creating individual power cables split off of main 14awg branch , route each of 60 connected ics.

this first problem comes in.  believe splitting large spi daisy chain smaller sub-chains power influencing spi communications (the data gets garbled) due different ground potentials @ each ic.  is method of splitting power bad, , if so, why?

i saw blog post other day guy had done daisy chain ground wiring way have... , found connecting end of chain main ground line fixed it.  example, in schematic connect , d main 14awg ground line.  i tried , spi comms improved... doesn't create ground loops?

i'm thinking should bite bullet , wire individual ground each ic main branch, take lot of work.  i want check electrical experts before starting don't waste time.  thoughts?

now second problem grounding arduino can communicate ics on spi line.  currently, have arduino ground wired 14awg main branch outside of project enclosure.  not work; spi data gets garbled.  if open enclosure , attach ground main branch close ics, work.  why length of ground wire matter in application?

in current setup, have attach arduino ground main branch because arduino being powered laptop.  understand creates ground loop, believe may answer previous question.  if power arduino directly 14awg main branch, believe can eliminate ground loop.  i'm going try when home,  guys think help?

finally, if powering arduino same supply ics won't work, believe need isolator spi lines.  do guys know of isolators 1-4mhz spi?

thanks again of guys, , sorry long first post.  had many questions , wanted make sure guys had details needed.

quote

1.  i cannot daisy chain power many ics.  the amount of current builds each ic in chain, , 22awg wires , pcb traces cannot support current.
2.  i lazy, , didn't want spend week creating individual power cables split off of main 14awg branch , route each of 60 connected ics.

what f?  ics?  what type?  pcb assemblies?  how current each 1 drawing?

the spi bus includes clk, mosi (so output arduino only?) , ss line each of f?

how long power , data cable runs?

what decoupling capacitors have fitted on f?

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