Decreasing Yields - What is going on?

You know, i think this is pretty simple. The only thing you have changed is the lights. If you truly havent changed anything else, then without a doubt, it is the lights.

Aeroknow said:

If you have magnetic ballasts, replace the caps in them. They fade with time.
What brand bulbs? And how old are they?

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I somehow missed your question.

Ballasts are less than 2 years old and one is only 6 months old. The lamps are Philips Cermalux. Same lamps I've used from the beginning. These lamps are brand new this cycle.

bigsteve said:

Theory 1 -- The only major variable you have tweaked is the lights, so my vote goes here.
Theory 2 -- I have experienced the exact same phenomen with my perpetual grow in 2014. I was around the 12th generation of Blueberry Gum from G13 Labs and my clones started to get smaller and scrawnier. Problem was I hadn't tweaked any of the variables on my commercial grow. Why mess with a good thing, eh? So, I'd suggest trying some plants from seedlings and grow them alongside some of your clones. See for yourself if the clones thrive as well as the seedlings.

Finally, I discovered that a good flush 2 weeks before harvest seems to up the bud size a bit.

Good luck, BigSteve.

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This would be the 6th generation of clones from clones, if that helps.

They rooted well, did fine in veg. After the flip they did not take off like they usually do. Not stunted or unhealthy looking... they just didn't get big or bulk up as usual.

I always flush, and did so this time. I use Advanced Nutrients and they are always fresh every cycle. I use it too fast for the nutes to get old. The nutes stay outside the room, which is never over 72F anyways.

I'm considering getting pulling out the glass hoods and going back to the open lamp reflectors for the next grow. I'll have to drop back to 3 lamps so the heat pump can keep up. I still have the old reflectors.

The thing that bothers me is the first grow with them wasn't bad. Down a little, but not like the last one. If I could think of a variable that changed, other than the hoods was the low night time temps. I did not think it could affect it so dramatically.

The light pattern is definitely different. It does not cover the area the other reflectors did. In the previous cycles I noticed the plants immediately under the lamps were the best. This time even this was absent.

Not sure if I missed any more replies.