Ya know, that usedto happen to me all the time, and everyone told me it was perfectly normal. Granted, it never hurt a thing, BUT, I think there's more to it, than that. I am still testing my theory, but am almost certain they they are a little hungry for nitrogen. The droop right after a heavy watering, because the soil is too wet, limiting nute uptake. They droop when they are getting almsot to the point of needing watered, because a good portion if the roots are in dry areas, and not able to feed. Then, there's the general drooping, for no real reason, other than a simple lack of nutes. The thing I've found, is that no matter what the situation, a foliar feeding with veg fert, will perk them up, happy as can be. That tells me that they are a little hungry. Maybe not to the point of possible deficiency, just on a limited diet, so to speak. Common sense will tell you that this'll slow them down, a little.
The reason they are perked up the next day, is that they had time to store nutes during the night, enough to keep them happy for some, or most, of the day. During 'lights on' the plant is still absorbing nutes, but not quite enough to sustain happiness, being that more are being processed, at that time. Therefore, when the nute supply dips below demand, the plants will droop.
That's my thoery, anyway.
Nah, I'm not familiar with BMO nutes, but, I can say that if they're compatible with other ferts, that they can be used together for foliar feeding. 1/4 + 1/4 won't be too strong, if that's what you were worried about. I used mine at full strength(both Dynagro Grow and Calmag Plug) without issue. The main thing you want to remember, is to hit the with straight water, the next day(or, within 3 or 4), so that nutes don't get built up on the foliage. The excess, will either be absorbed, or washed off. Both helpful. 
