Thank you in advance for the help!

I got a Juniper bonsai for my boyfriend's birthday, we've had it for 3 weeks. As you can see, the lower and inner leaves started turning yellow, they are looking a bit weak too. This started under my care, which hasn't been perfect... I'd appreciate any advice.

Two pics of the yellowing parts + the third photo in natural sunlight shows the bonsai right when/before the yellowing started, and this is also where we keep it. This is the strongest light it gets.

I'll try to give as much detail as possible below.

Environment
- We're in DC, humidity has been medium (~60%), temperatures range between 55F at night and 82F during the hottest days. The past two weeks we got a mix of overcast and sunny.
- The tree is indoors, about 1 foot away from floor-to-ceiling windows looking North-Northeast. The apartment is relatively light all day, we get direct sunlight for about 3-4 hours in the morning. The window next to it was sometimes open the all day and night, sometimes it was closed and the HVAC system was working. The HVAC is set on 72, but I took advantage of being home alone and turned it off for the last two weeks.
- I can't tell you what kind of soil it's in, but we got it from a bonsai shop (I won't link because it's not Bonsai Empire) and we did not repot it yet, nor did we give it any fertilizer.

Watering
The first week, my boyfriend took care of the tree, gave it about 20 ml water in the morning and at night. It seemed to be happy with that, although I was worried about root rot – we knew that bonsais need a lot of water, but I've overwatered plants before and wanted to be careful.
Then, he was away for the past two weeks and I was taking care of the tree.
I was still worried about overwatering, and I also just... forgot to water it some days maybe 3 days total, but never consecutive days. To make up for that, I gave plenty of water two times, and sprayed the leaves as well. Every time I gave it water, the soil was dry and hard.

Discoloration
Since I wasn't paying perfect attention to the tree, I'm not completely sure if the yellowing started when I missed watering days, or when I gave the tree lots of water.

Any advice is much appreciated!!
Thanks
Ella

Your tree seem healty to me. You lost one branch, could be from when you bought it. Snip oft the dried branch. Water when top layer starts to dry. And when you water, water it until the water flows out under the drainage hole in the pot.

The tree is indoors! Junipers cannot grow indoors. Bring it outdoors.

My bad. Procumbens nana must be outdoor.

All junipers must be outdoors.