It sounds like a nitro issue , but did you flush BEFORE going into flower ?
You want to clear plant of veg nutes because you will be using flower nutes that are lower in nitro. It can be fixed. Stop what ever you were feeding . If plant hasn't been watered yet , do a flush approx. 2 or 3 times the pot size that your plant is in .
You want a clean slate to start new regime of flower/bloom nutes.
Allow plant to recover from flush before starting new nutes.
Don't put back into veg , you will be fine , just get her ready for flower by clearing previous nutes.
No STANK NO DANK