Those brown parts are remnants of the sheath that protects the new leaf while it is forming and emerging. Totally normal you can leave them there. You'll want to give it a lot of water over the sink so it can flow out unabated. You'll also probably want to change to a glazed or plastic pot to hold in moisture. Clay pots such as the one you have this plant in are very porous and evaporate water very quickly, maybe faster than you'll want to spend time watering it.

Difficult to say what exactly is the cause. There are two easy to notice mistakes you did though: first, the plant is buried too deeply second, you should always water immediately after re-potting, otherwise the new, dry soil will suck the moisture from the old soil the plant was in. Either one, or both of these mistakes could be the cause, or at least contribute, to the yellowing. .

Is that the only leaf that is yellowing? Probably the oldest leaf? Do not worry about one leaf. Are the rest of the leaves less perky than before. Roots grow differently in soil than in water. I prefer to root directly in soil and mixing soil slowly in the water doesn't help the transfer. The plant actually has to grow new roots or at least new root tips into the soil mixture to take up the moisture from it (the soil). That takes a little adjusting and the plant it a little stressed during the process but should be fine. I hope you are using a nice open mix.....one that stays moist but has a lot of air space (e.g. extra perlite and/or bark (you can add orchid mix) in the soil). keep lightly moist. If the plant get real limp you can get a large clear bag and put it around the plant to raise humidity for a few days while new roots get established.....than gradually open the bag over several days. The lighting look probably good..........very bright but no direct southern sun mid-day (mornign or late day sun ok). Never fertilize a newly transplanted or potted plant. Later when it begins growing new leaves you can start some light fertilization but not now. Soil should never be soggy. It should be slightly moist (but have a lot of air space in it, as I mentioned above). Later when it is rooted in you can let it dry between watering.

Yes green balls are fertilizer. you said no repots, so Im guessing plant is still in its original store soil. Those are usually way too water retentive. A lot of people on here either use Al’s 5-1-1 mix for tropical or soil mixed 50% w/ 50% sifted perlite or pumice. 5-1-1 has 5 parts pine or fir bark, 1 pt. Sifted, coarse-grade perlite & 1 part peat. The issue w/ your Monstera looks like bacterial leaf spot from too wet soil, but I could be mistaken.. others on here may be better at diagnosing. These grow under trees & climb their trunks like a vine in the wild, south of the equator. Your water & sun accommodations sound good, as long as you keep it where it’s at, that light would be similar to what it wants, which is part shade.