Caulerpa ???

I have a sword like caulerpa at least thats what I've been told...It's in the photo and been in my tank since the start...It's been happy and growing and I cut it back when I get to much...
The last week it's been turning clear from the top down (also in the pic) I'm having a feeling there is something going on I'd like to "NIP IT IN THE BUD" Do you think it could be the PH..I know it's abit low....

My feather duster has gone into his tube for the last week or so also.

My clowns and Green-e (mandarin) are happy...
My yellow polyps are growing and having babies...
My shrooms are growing and having babies...
Water
PH 8.1
Nitrite 0
Nitrate 0
Ammonia 0
Phosphate (tinge) couldn't really come up with a number

 

my chateu started turning clear in my fuge so i extended my light cycle and it came back. also any kind of a slick or coating on the surface of the water can affect light penetration.

 

caulerpa prolifera needs a good amount of nutrients to keep going, it may just be starving a bit. do you prune old growth or new?

 

I've been pruning the new growth...I'm sure the light is on long enough...maybe to long if anything...Could that be a problem?
Is there a specific nutrient it needs?
Should I cut it way back?
My grape is doing really good and I cut back the new growth on it as well.
Any suggestions are welcome...