Couple of things you can do. You need to change water every week and put distilled water. Wash the roots while changing water. You can also put some coco peat so that nutrient uptake is proper. Lastly the smaller bamboo needs lot of care and if not given then can wilt soon so next time you can go for slightly bigger Bamboo's #advice
Suggest you throw them away as they are diseased and can impact others in the group if you have more stalks still going strong. Alternatively you can cut all the soft part and plant in a separate pot #advice
They ought to. Just make sure you keep them in shade. They do not need direct light at all. I’ve had mine for close to 3 yrs now & I got them from HD hehe 😉 good luck with yours. I hope they bounce back!