If this has been asked before on here I'm sorry for asking again, but I can't find it

I have been growing now for around six years and in all that time I have never changed the bulbs for new ones. I am using a 400 watt system and I use a metal Halide bulb for the vegative growing and switch to a high pressure sodium for inducing flowering.
Now in all this time I have had rather good results and some decent crops, however the last crop was totally wiped out I suspect due to a blight of some kind, but I have noticed also the last few crops have been declining in there yeild and the plants have be getting a little on the slow to grow and puny side. Well I an not sure if it's the seeds or something else causing this?

The question I would like to ask is do the types of bulbs I am using require replacing at certain intervals, do they start to deliver less of the correct spectum of light with being used for so long?

I have tried everything to put things right, the only thing I have not done is change the bulbs, thats why I am asking this question.

Thankyou guys ..........................love mand xxx
mand Reviewed by mand on . Bulb changing If this has been asked before on here I'm sorry for asking again, but I can't find it :o I have been growing now for around six years and in all that time I have never changed the bulbs for new ones. I am using a 400 watt system and I use a metal Halide bulb for the vegative growing and switch to a high pressure sodium for inducing flowering. Now in all this time I have had rather good results and some decent crops, however the last crop was totally wiped out I suspect due to a blight of Rating: 5