Question
QUESTION: Hi , I have a small Coleus plant. It has the 'Green' (outline) and Red(center) coloured leaves. Since yesterday I am seeing the 'green colour has changed to yellow' and not just the  green even the red has got yellowishness in it . In other words the leaves are becoming yellow and they are falling off the plant. A lot of leaves have become yellowish and are ready to fall off (but they're not brown or dry but are weak and dull ). I shook the plant just to check and around 20 leaves fell off. Now today i think 60% leaves have fallen and my beautiful plant looks very bad and weak even though the soil is moist . They're becoming brown only after they have got separated from the plant . What should i do now to save my plant , i don't wanna lose it. Please Help.

ANSWER: The symptoms you've described sound like the plant has received too much water.  When this happens, the roots become saturated and literally suffocate the plant.  The leaves then discolor and eventually drop.

Allow the soil to completely dry out before watering.  Then water deeply until water seeps from the drain hole. In the future, only water when the top third of the soil dries out.

In all honesty, depending on the severity of the problem, it may be too late to save this particular plant.  All I can do is recommend what I did and hope that the plant survives.  But in the future, please follow the watering techniques I've outlined above.

Good luck, and enjoy your weekend.

Mike

---------- FOLLOW-UP ----------

QUESTION: Hey thanks for advice but i want to save this particular plant . It's still has around 40% of leaves remaining which aren't discolouring, indicating that some roots are not rotten and the plant can still be saved so please tell what things i need to do now. Ever Since i asked that question i watered it only once that's 1 day after asking and it's soil is dry(rock hard) since 3 days now . Should i water it now or not , if not then when should i ? Secondly should i take plant out of soil & repot it in same soil after removing rotten roots. But to do that i'll have to water it only then it can come out. What to do ?

Answer
Now that the soil is dry, go ahead and water deeply every few days once the top 1" of soil is dry.  Do not fertilize for a couple of more weeks.  At this stage, you have to wait for the plant to recover on it's own.  The more you do to try and help it, the worse it will be.  

Plants are resilient.  As long as the plant still has green to its stem and leaves, it should recover nicely.