bald patches on lawn newly grown?

It sounds like it is web from spiders. I have the same thing on my lawn

you could have a fungal disease call 'brown patch ' you need to treat the area with zineb or captan ; if your unsure of this jargon , go to your local nursery . but it may simply be that you are over watering your new lawn , combined with too close a mowing pattern and poor drainage . anyhow see how you go and good luck