Almost successfull grower needs help...

3 plants- 3 weeks into flowering (12 &12), all 3 are in the same 18 gallon storage bin, have used orchid bloom booster ( 10-35-15) 1/4 strength twice in the flowering stage, and have used Superthrive in every watering.
Problem: plants are very pale green and losing color
I fed them last night hoping it was lack of nitro, but they are still very pale today, do i need to add some of my veg nutes to bring up the nitrogen? first grow and they look great to me, plenty of buds w/ long hairs have formed, would hate to lose em so close to harvest
working on pics....

Pics would be helpful, but it sounds like it doesn't have enough nitrogen to me... I'm a rookie though, so the vets will probably be more useful to you. I hope it all turns out well, man.

here's a pic of one of the plants in question, any advise?

More information is needed in order to help, like soil or hydro. Apicture of a single plant might help also. Lets assume hydro since you talk about daily watering. If its soil and you are watering daily that could be the problem.
IF IN DOUBT FLUSH IT OUT!!. INSTEAD OF TRYING A LITTLE OF THIS AND A LITTLE OF THAT. 90% of the time that will cure it, and it will never kills them. You do this by using 1/4 strength nute solution at 2 times the watering capacity of your pots. Then start over with fresh solution, phd water and the proper ppm for your nutes.
Having said that, I haven't ever had to flush my plants. I check my ec of all of the tanks everyday and add water back to the original level. Change the reservoirs every two weeks. If you do it right to start with, you won't have any problems to fix. VV