my avocado tree is a little over a year old and currently about 2ft tall. It was doing really well for a long time,growing faster than I could track with green/purple-wish leaves. About a month after I planted it in soil it stopped making new leaves and started growing the existing ones bigger and bigger. I tried cutting off the biggest leaves but it just did the same thing with the others. Then two things happened. 1.there was a soil gnat infestation and 2 winter in massachusetts. There is not nearly as much sunlight in my dorm room as my home but I bought a plant light and moved it in front of the window today.In both residences the winter temp stays between 60-70. Rarely above or below. I was able to kill off the gnats with nematodes last week but I'm worried the combo of root damage and winter might be the end. It hasn't grown at all in the last couple of months and the leaves are turning brown. (I do a deep soak about once a week for watering.)

If anyone can pinpoint the problem and help me save it it would be greatly appreciated. Tips are also helpful since this is my first avocado plant. Thank you.