this is what I have been using for years
Pohl's K-Balance Potassium Concentrate
if you cant find that thrive is another cheaper alternative

PM me, I have tons :D

Thanks alot is that a diy or Comercial brand

Sound it at BRS, 33.99 for 250 ml does this stuff go along way?

Yes

Tested my K and it's around 370 using a salifert kit. Is this low enough you think to be causing my problem ?

Hmm, that's not far off from optimal range (380 ppm).

Try moving it to another part of your tank. What bulbs are you running and how old are they?

they are around 5 months old but when i first got it the colour was bad like a dark brown grey . now is super light.