Humidity would have been my first guess as well (assuming proper watering). Do you have forced air heat and/or are they are getting a draft? And did this start after the sub-zero cold snap we had (furnace running more)?

tj

I used hot water heating, and I don't believe that the furnace is running more. Do you think I should try misting the leaves more often?

I, too, have hydronic heat so drafts aren't the problem. You may want to try a pebble tray. Get a tray wide enough to hold the pot your plant is in with room to spare, fill it with pebbles and just enough water so the pot doesn't wick the water up. That should raise the humidity around the plant a bit.

tj

Do you think I should try misting the leaves more often?

Sorry I don't have any answers for you, but wanted to say that misting plants has next to no affect on them humidity wise. If you consider how long the mist lasts before it evaporates into the air it is probably minutes. That is as long as the benefit lasts.

A better solution to the humidity issue would be a pebble tray underneath and if necessary a plastic bag with holes put over the foliage (to retain humidity).

Do you fertilize over the winter?

thank you for the tips!, I fertilize every 2 months in the winter with a very mild fertilizer, half stregnth miricle grow, but in the summer every month. should I use a slightly acid fertilizer, similar to that for azaleas?

The Miracle Grow should be fine, but if you wish to have the fertilizer solution acidified a bit just add an ounce or two of vinegar to a gallon of water. It generally doesn't matter much in a container like it does in the soil.

How long has the plant been in the same potting mix and is this a commercially prepared mix or one you made? The reason I ask is that Calcium and Magnesium are plant nutrients not supplied by Miracle Grow. Most peat based commercial mixes have had lime added and lime adds both Calcium and Magnesium, but after a year or so most of it is washed out or used up.

There are a lot of plants that don't do all that well inside over the winter even though they thrive in the summer though. Could just be 'winter blues' for the plant. Less humidity, lower light levels, shorter duration of light, less air circulation etc.

I have a coffee plant, also. I can tell you what seems to be working for me. Mine never gets full sun, it gets a little morning sun and that's it. In nature they grow under a canapy. It is by the kitchen sink and only gets fertilized sporatically in the winter with a very very mild solution. I let my house get down to 55-57F at night (most plants love that) and to about 68F during the day. It never gets misted and gets watered only when the soil feels dry.

So far this method had been working for my situation.