high salts indoor plants
There are a few possible answers for the browned tip; the simplest could be when you moved your plant back to the window, the tip may have been touching the glass and either got burned or even the opposite, frozen or just too cold.
More commonly for house plants is high salt, salt buildup in the soil. The salts come from fertilizer and/or tap water from the city water municipality. Dissolved minerals, fluorine, chlorine and fertilizer that you have added.
I'd like to see the top of the soil better, does it have a white powdery crust? If you were using clay you could easily see the white salts on the rim and sides of the clay pot as well. Are you 'misting' your plants? The spots and white coating could also be indicative of high salt in your water.
This is good to notice so quickly. High salts will eventually kill a plant, some plants are intolerant of any salt will die very quickly.
Did you use potting soil from a bag, hopefully? With no added fertilizers or water holding sponges/gels?
I would recommend repotting your plants in fresh bagged potting soil. If you've recently changed out the soil you should take your indoor plants and put them in the shower. Put a screen over your drain just in case errant debris and soil gets loose. Use cold water only and allow your plants a good 5 minutes of 'rain'...even though it is tap water. Then allow your plants to sit, drain for half an hour and turn on the shower again for another 5 minutes. This leaches salts that have built up in the soil, cleans dust off leaves. Misting does nothing for plants, this shower does wonders. I do this every few months. I also put all my indoor plants out on a covered, shaded porch for the summer months. They get better light even in the shade than they get in the house. This allows them to make more food to last them the winter. Rejuvenates indoor plants. Once or twice I turn the hose on the entire plant and pot and soil on the porch during the summer.
Indoor plants in pots have only the little bit of soil given them in the pot. Garden soil or composts have who-knows-what in the shovel full you would put in your pot. The larger garden soil environment has its own 'controls' for fungal spores, insect eggs, virus, bacteria but one shovel full could be just insect eggs or one fungal spore...that will have no controls in the amount of soil plucked from the garden.
If you used potting soil then great, otherwise, I would repot using sterilized potting soil out of a bag. Cheapest one works great. No added fertilizers, no add moisture gimmicks like sponges and gels.
To repot, take your plant out of the pot and lay it on its side on newspaper. Cover the root ball with a bit of newspaper while you clean the pot. Good time to inspect the roots; are they bright white? Are they encircling the root ball on the inside of the pot (get a new pot 2 to 4" in diameter larger)? For clay pots soak the original pot first for a few hours. For all pots scrub with a little bleach, rinse and dry. It is then ready for new soil and a plant. No rocks or gravel at the bottom...this is important. Just potting soil. Lift bottom of pot off surface of saucer or patio with 'pot feet' (cute) or just pieces of tile. This greatly aids drainage. Never allow pot to sit in a puddle of water.
Please tell us what you've used for soil, fertilizer, type of water (you could also use distilled water...bottled water comes with fluoride a very bad chemical waste product...heck even can goods, soft drinks, gatoraide, breakfast cereals have fluoride). Definitely look this up for your own health...fluoride is bad for plants and bad for all living things and bad for teeth, never meant for health! Fluoride is not just fluoride but a number of nasty chemicals some not even named, to include lead and arsenic. And Fluoride (Hydrofluorosilicic Acid) gets stored in your bones. Plants take it up, store it in their fruits, leaves and roots and if we eat those plants we get even more fluoride to store in our bodies.
This burnt leaf tip could also be indicative of chemistry (fertilizer) imbalance or deficiency. A deficiency of Potassium or Zinc. Or an excess of Potassium will cause a zinc or iron deficiency.
Send a picture of the entire plant, please with the pot and soil. Thanks, hope this helps.