Problems:- The first thing to do is Don't panic! Ask your self these questions

1) What has changed?

2) Is the soil wet?

3) Have you been feeding the plant? If so, what with?

4) What is the night time temperature?

Once you have the answers to these questions, see how to resolve them.

1) What has changed? Have you moved the plant, If inside check the temperature and Most importantly the Humidity. The Best temperature to aim for is 70-90F in summer and no lower than 50F in winter. Below 50F the plant stops growing and therefore stops taking up water and food so these must be stopped.

As for humidity citrus dislike the modern day centrally heated room as most of the mosture is removed. If you have no other place for your plants then look for ways to increase the humidity e.g. fill the pot-stands with pebbles and keep wet.

2) Is the Soil wet? if the night temperature is below 50F then stop watering now, if possible increase the temperature and leave the plant alone - if the soil is staying wet try removing it from the pot, turning the pot upside down and let it dry out by sitting to top of the pot.

3) Are you feeding the plant if so, what with? - A feeding pattern must be started, in the UK this seams to be totally different than anywhere else and this is the scheme I have adoted. Feeding in Winter is just as important as summer as the plant needs to continue the development of the fruit and keep the plant strong for next years crop. Stay away from high potash food (Tomatoes feeds) In Summer the plant needs nitrogen to grow the best feeds are ones with an NPK of 25 15 15 with trace elements. In winter look for and NPK of 20 20 20 and again trace elements