I have a small mango seedling planted from seed.

Often (twice so far) new leaves will start developing only to brown out from the tip and die (see photos). Last time this happened, a new leaf (top grown one currently) developed fully following the burned leaf. Now, a new leaf started emerging only to brown out again.

I'm open to suggestions as to what the issue may be. Only thing that comes to mind is temperature. I live in a zone 10a area (Low temps around 5C in winter, but can reach as low as -1C on occasions) which is slightly cold for a mango tree, so the pot was moved indoors for the winter. It's worth mentioning that the last healthy leaf developed once it was moved indoors. Now (Current Temp is around 19C-9C) it is still indoors, but gets some outdoor training due to it being placed by the window which is sometimes open.

The pot is usually left to dry out, then gets a good watering. No fertilizer has been applied. This plant sprouted around mid summer last year (it's 8 months old now ).

Any tips/observations are welcome.

Thank you.

Edit: I've added a third photo which shows the bottom leaves, two of which have had some burn along the way, in case that helps.