"6 40watt 4ft tubes" at what distance from the plants, and with what reflector? 40W T12 bulbs (I'm assuming that's what they are) put out about 1600 lumens. Six of them, therefore, will put out 9600, which is sufficient to burn plants, so more than enough for blooming, if properly placed.
I used to grow exclusively under lights, and had no issues with catts or vandaceous plants, but intensity hitting the plants is crucial.
I did some measurements of a 24W T5 bulb, with and without a reflector. The output of one of those is 2160 lumens, and I measured 2000 fc at the point where the reflector flanges end (about 1" from the bulb itself). At 6", it was down to 800 fc.
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