Arthur, I'm sort of new to the starters, but I think your photo series looks fine, nothing to necessarily indicate contamination. I've had mine going for about a month and a half now, and take them out of the fridge on weekends to make them happy.
I even mistreated them badly recently, not feeding them for close to two weeks. The hooch layer got really thick, and I took them out and fed them... But had to make room in the fridge and off the counter due to turkey day. So into the garage they went, ~38F at night for two days. Oh, they were pissy after that.
Really, a lot of it is intuitive, I've found. You just get a sense of how happy they are, and your nose is a great indicator of that happiness. I have the Camaldoli, the Ischia, and the French, and I was afraid there could be contamination between the various starters, and I'd wind up with three identical ones unwittingly. But my nose says otherwise. The French remains the mildest, the Camaldoli has almost a sweetness to it, and the Ischia is my workhorse.
I never made a proofing box, but found a seedling starter mat heats the starter well enough. When the starters are really grumpy, I'll get them back to happiness by literally sweetening the pot a bit, giving them about 1/2 - 1 t. honey, depending on how grouchy they are. After that, straight feedings. Just started proofing a pizza dough from the Ischia, and despite the abuse, by morning it was bubbling with zeal.
Just be patient, don't freak out, and allow yourself the insanity of anthropomorphizing them slightly, letting them seem to have personalities.