These cactus need much more sun - you should slowly (over two weeks) acclimate them to much more. They're also in unsuitable soil (we won't get into the intricacies of that here) - suffice it to say that if you cut that soil with 50% perlite, repot them in the amended mix, wait a few days and then give them a light watering, warmth, and increasing amounts of sunlight over a fortnight or so, your plant will start to grow better. You're better off slicing the abnormal upper third of those plants (they might be Mammillarias) with a sharp, clean knife and letting the cut ends heal.

I don't do moon cactus (in fact, my suggestion is to never have them, and yet I'm foolish to think so...), but it sounds as if it's dead / dying (squishy is never good in C&S, but sometimes plants can be salvaged).

Inadequate light, improper watering (combined with the unsuitable soil) - all these things contributed to El Squishy. Plus you're growing inside (almost all cacti want to grow outside, at least when the weather's cooperative) - that's a whole litany of future doom for these plants of ours.

Winter's around the corner, so if you live in a cold area you'll have to keep these inside. The more light the better, and you'll want to lessen watering to a minimum (they generally don't grow much in winter).