Interested wrote:

hi ....

i hv observed that some of the plants, including java moss in my tank has
seemed to "shrink" in size. when they were bought and introduced into my
tank 5-6 months ago, they seem to be doing well - green and vibrant.

now they have they have shorter stems and leaves. in the past, i used to
prune them every 3 weeks. now, i can wait till 4-5 weeks. as for color, they
are still green and growing - reacting well with light and CO2 - oxygen
bubbling still occurs. fertiliser wise, i'm using liquild formula bought
from LHS.

Without details on your water parameters, fish load and type of ferts, it's
impossible to say.

However, what you describe sounds like a classic case of plants using up a key
nutrient in the water, which is not being replaced by your water changes (you
change water ever 1-2 weeks, right?), your ferts or your fish waste.