If your deficient, why would you want to flush? To wash away more of what's lacking?
Do you know how rare a MO deficiency is?
I'd be looking elsewhere for the problem, but if you hit he plant with some micro nutes, it will take care of the MO, if that's what it is. I use Earth Juice Micro-blast, but there are many on the market.
Upload pics. Droopy's right MO deficiancy is rare according to my literature. Picture's worth. Thousa words. What strain is this? What type of media (brand, blend + ammendments)? PH tolerance varies from starin to starin species to species. U may be experiencing a PH problem. 6.5 can be high for certain strains. If you decide to flush, I'd flush with half strength nutes (depending upon the growth stage).
What size pots? What growth stage (veg, flower)? How long in that stage and how tall are plants? I'm trynig to get a feel fot the size of the plants. How long have they been in the pots they're in? Can u upload and post a pic or 2? It wouuld help us help u better.