Advise on flowering

She may be maturing differently is all, although she looks like she could use some calmag. She may just stretch later than the other two or it could just be gentics. If you have one whose buds arent fattening, consider cutting back on any feed with N in it. You may be encouraging more growth and less bud development. Last thing-- don't flush! It doesnt do anything but rob your plant of nutes when she wants them the most. There's nothing that you can do to change what is already in your plant. The salts arent gonna evaporate or leech back into the soil or be broken down. Hard to swallow, trust me, I know, but check out the science on it. Flushing gives you a smaller yield and worse tasting product. Anyway, good luck!