It looks like mechanical damage to me. The rest of the plant looks great, and I would expect similar damage to other leaves if it was being underwatered..

Water depends on where it's kept and sun, and temp. When warmer out or in much more sun, the plant will need more water. As long as it's warm out where your at, give it more water but never let it sit in water.

The soil looks very peaty which may not be a problem with you. For some it is since that mix will hold on to water much more. Over all the plant looks okay to me. It looks like you will have some new starts (pups) coming up. I would leave alone and let it fill the pot up.

Thank you very much guys, I've watered the soil (not too much, as usual) and I'll keep the plant under observation. If will begin to deteriorate more, I'll use these two leaves for propagation before it's too late. So far there are no signs of going worst, we will see.

All the best, Sara

Hi, the plant was dry. Just wanted to let others know :)

Now it's fine, new babies are rising. Thank you again!

Thank you for responding back Sara. Good to know. Hope you show us some pictures soon.