I have 5 hibiscus plants that look great, and has many buds, but will not flower. It doesn't even drop the bud?

instead they keep growing more. Should I cut the buds off to make room for healthy new ones? I water & feed them with acidic fertilizer & have them in different locations through out the yard. I also have a hibiscus tree that was beautiful in my house all winter & that is looking sick & not flowering outside either. I do have to say that besides one 103 degree day, we have not had any warm weather over 80 degrees up until this week. I have had many hibiscus through the years & never had this problem before. Someone please HELP!