Answer: This sounds like a lack of phosphorus. Your soil may not lack phosphorus, per se, but it may be locked up in the soil because the pH is off, or due to lack of soil organic matter and moisture, or soil that is very cool. To find out for sure, have your soil tested, either professionally or with a home soil test. If you just recently transplanted broccoli seedlings, they may be feeling some transplant shock, too. Their roots need some time to adjust to the new soil environment, and until then, the plants won't be able to absorb nutrients efficiently. It may be helpful to spray the leaves with a seaweed or kelp and fish emulsion fertilizer (follow label directions). Best of luck!
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