Dear Sir / Ma'm, if bonus marks are to be awarded, then it will definitely be declared by the NTA in an official notice. Candidates can challenge the answer through the official website after the release of answer key. The NEET 2019 official answer key is likely to be released by May 30 and challenge can be made within about 1-2 days, which will be informed once the OMR is uploaded. After all this, if NTA feels, grace marks should be awarded, it will do so. Till now, there has been no news as such.