i never used the cleaning carts..... syringes are necessary with this type of printer as you need to pull the ink thru once in a while.
Anyway... if ur seeing some deflection in the working part of the print head and the middle is gone on BOTH the heads then I am thinking that it is pumping. Got to be hasn't it? other thing it could be is not a perfect seal which can happen to the caps. I think this is a JV3SP machine as I am more used to the JV3S, so I am not sure on ur pump/capping configuration.
Another thing to check, is ur waste full? can you do a disway wash okay where u drop fluid in the caps and it gets rid of it down the pipe... if u take the tank bottle away and do disway wash (warning: ink splashes) then see if it dribbles out of the tube, that give you a good clue if your blocked.
But I wouldn't waste much time... get straight on it... time is ticking to sort it before the head is blocked. I find it strange that you lost all of these at once.
If you pull the ink thru the lines easily... and it shows all the nozzles then u know the head is okay but if u then start using the machine and it blocks again, then u know its sucking issue