Interesting as the SS hoses (by the little yellow band around the rear left I might assume it's a Goodridge G-Stop hose which is considered the best) are definitely not supposed to cause a spongy pedal. I just bought a set and the box states to not mix the two types.
Rubber hoses flex under pressure whereas the SS ones do not, leading to a firmer pedal feel.

Just yesterday I was going to replace the rear rotors & pads and install all new SS hoses. It was 98°F outside, bugs were having me for dinner, and I just couldn't get that first rotor off of the hub. It's on there and I do mean good. I tried to then undo the top fitting for the brake hoses by using a modified box end(the line wrench set I bought curiously lacked an 11mm) and it slipped on the hex. It slightly marred the nut but not enough to ruin it. I took all that as a sign I should put it back together and take it to a shop. I hate it when that happens. Bought a Motive bleeder and everything.

Another thing I've noticed about your setup is the rear rotor seem to be vented, and these cars have solid rotors stock. How does that work? Seems like the vented rotors would be too thick for the calipers.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)