I appreciate your concern and asking on HCM.
I would suggest the following:
1. It is important to look into the cause of the academic decline. If there are some associated
stress factors or emotional disturbance that needs to be addressed.
2. For memory improvement you can take the following measures.
a. Improve your attention. Only those things go to memory to which full attention is given.
b. Rehearse the information for some time to get it into short term and then long term memory.
c. Study in short spans.
d. Store information in chunks and memorize the main concept first and attach the associated concepts.
e. Use example, flow charts, diagrams to improve the retention of the particular concept.
f. Use mnemonics for lists.
g. Recall after you have read.
h. Make questions of headings and read to find the answers.
I hope you find this helpful.