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Can you post some pictures? It would also help to know how you've been caring for it--what sort of light does it get, how often are you watering, etc. In the absence of pictures and other information, my first guess on plant problems is always overwatering since that's probably the most frequent thing that people do wrong with their plants, but it's impossible to say for sure without having more info.
I agree with Ecrane, you need to give a little more info so people can help you out,
How long have you had the plants, what type of soil are they in, do you feed them, are they allowed to sit in saucers full of water, Most important, have you recently moved the plant that is in bud, they don't like being moved around when in bud, it seems to stress them and they can drop either the buds or the whole leaf.
the soil needs to be free draining, I like to mix a 3 hand trowels of shop or home made compost, 1 off horticultural sand and 1 off fine gravel / Grit, you can buy the grit / sand from garden store like DIY plant area.
Don't re-pot while the plants are in bud or they will be even more stressed but if you can, give us more info on how your growing them for now.
Good luck. WeeNel.