Hello everyone, this is my first time here, and I could really use some advice! See attached pictures and at least read the last 2 paragraphs for shortest version! We have a dwarf variegated pink lemon tree, that was given to my husband about 12 years ago by a close family member who passed away about 6 years ago, so this tree is very special to us. Being in Ohio, every year we put it outside during the summer, and then acclimate it to be back inside over the winter, and we have never had any problems with this tree, until now. In the late spring last year we did re pot it because it needed a larger pot, but that has been the only change over the years: every winter it goes in the same room, on the same table next to the same window. All the sudden about 2 weeks ago the leaves started shriveling up, turning brown and dying. It looks as if the tree is just dying! We can't see any evidence of any pests or mold type issues, although we haven't completely ruled that out. Its also in a room with a fish tank which seems to provide good humidity, again, the same exact environment it has always wintered in for the past dozen years. The branches are dying, its just dying and I don't know what to do! My instinct is to prune back the dead stuff, but I always worry about wrongly pruning it. The absolute only change to its indoor environment is the addition of an African Violet to the plant table, and my orchid just finally re-bloomed, which makes me worry about some type of infestation. Anyway, sorry that was so long! What steps should I take? I feel like I should check the roots are healthy, prune back the dead bits, and possibly add a bit of epsom salt to the water next time? We have never checked pH, we've always had very successful gardens every year and I have never had a problem with a plant that stumped me, but since its been alive and healthy for 12 years, and all this year up until 2 weeks ago when the tree took this quite sudden turn for the worst, I wouldn't think pH would be the problem, and, if it were, I would think we would have seen more subtle signs of distress than this sudden dying. Any suggestions will be *greatly* appreciated!